There is a lot in here to go through and unpack. I will tell you from the beginning that if you don’t already have a psychologist (not a psychiatrist) that you trust and feel comfortable with, it will be very useful for you to start looking. Do not settle. There are a lot of amazing psychologists out there and there are a lot of shit quacks who just happened to make their way to a deploma. There will be some that are good, but they won’t be right for you. Figure out what you need help with and what you are looking for from them, but ideally you will find someone who helps you dig down and find all the truths buried inside of you–hidden away because of a variety of difficult emotions they elicit.
That said, I’m going to dig into your reply, though not in order.
I first have to ask you if you ever truly loved yourself to begin with. This is not meant to be harsh, but a gentle nudge to understand that past you–the one who was always so unselfish and who was constantly giving to others. Why were you always giving? Perhaps on the surface you might think, “To be nice,” or “Because I liked helping and making people happy.” And maybe part of that is true. But we do not become constant givers out of ultruism because children have a subconscious need to survive in the world and they subconsciously latch on to whatever it is that will make sure they do.
It sounds to me like deep down you were looking for your parents to be parents, for them to take care of you. That’s what every child wants and needs. Of course, should you not get that, should you spend your childhood being “the good child” (for a whole host of possible reasons), then you grow into that role into adulthood. Bosses, friends, lovers, and all manner of people become substitutions for you parents in that deep psychological way. Everyone responds differently to this. Some people spend their whole lives going and going, giving and giving (often in a deep state of denial). Some people break down and swing all the way to the other side in an attempt to take control of getting those needs, but they aren’t naturally selfish and it doesn’t end up feeling as good as they’d hoped, which can be even more devistating. Others might trial and error their way into self understanding, or might seek therapy. Maybe that lasts a lifetime; maybe just a few years. And there are so many levels between.
The point is that such an amount of selfless giving cannot last, as you know. My personal thoughts are that you might benefit from (probably many years) of digging down into the sludge of your psyche to find out all the whys (e.g. Why did I behave this way at this point in my life?), the whens (e.g. When did I start doing this thing, or when did I become aware of that), the hows (e.g. How did I get from this point to this point, when I started here?), and the whats (e.g. What happened at this stage? What event or behavior from another person could have affected me in such a way that I might have done/felt/responded/etc., in this or that way?)
Often we have deep seeded needs that were not met when we were children, but we don’t always know the core of them. Generally they boil down to something simple that might make us think, “This seems almost silly…” But those basic needs are far from silly and often become our core motivation(s) for everything we do in life, how we think, how we respond to people and situations, etc.
So, will you ever love yourself again? I don’t know. That implies you going back to something. I can tell you that I believe you can learn to love yourself as who you are and who you can become. I don’t need to ever meet you to tell you that you have more potential than you know. The work will be hard, but it will be worth it if you really want it.
As for forgiving yourself for your mistakes… I think that depends on where you go from here. Genuine forgiveness is a letting go. There is a releasing that happens. You know you can’t change the past. The only thing you can do is decide what future you want and make every moment in the now be a step in that direction. To do that, you will need to really know, really see this future you desire, and then you will need to know the steps to get there–from the big to the small. Forgiveness involves being able to look back on the things you did, accepting responsibility, and not having that same emotional pain that you do now because you have allowed yourself to learn from these painful experiences, to let them fuel your steps each day, and to know that those things were not a waste because of what you learned, who you became, and what you built. You also need to know how you will know that you have forgiven yourself. If you don’t know what you’re looking for, you will never know if you made it.
I feel like you need to learn “healthy selfishness”. This involves being able to say ‘no’ to things without feeling guilted into them. It means taking time out of your day for yourself. It means being honest with yourself about what you need to be your best self, and being honest with your partner about what you need and building up an open and honest communication with him–one that hopefully he will be receptive to and will be work on himself and the partnership. It’s possible the two of you may benefit from couple’s therapy. This isn’t something I could know, but consider it if you think it will be useful.
Learn to let people you love and trust do things for you, even if they’re little things. If you’ve been a life long giver, this might be hard–which could be part of why you swung so hard to the other side. It’s easier, in a way, to just take what you want, than to admit to what you need and allow someone to fill that genuine need. It might even feel uncomfortable because you’re not used to it.
I think maybe you got a glimpse of the father you might have always wanted when you were younger in those last four years. Now, I can only imagine how deep your grief must be concerning so many things. To have gotten this connection, only to have it taken away. This is another area where a phychologist you trust and feel comfortable with could be very helpful. And I pause here to say that there are other qualified guides in this world. If you’re religious, then you may find some healing through a genuine religious leader you trust. Or maybe you have an astrologist or a tarot reader who is able to give you some insight if this is your proclivity. All your help doesn’t need to come from one source or someone with a paper that proved they are hundreds of dollars in debt to have learned the works of Carl Jung. If you’re a reader, start reading books and you may be able to do a lot of work by yourself.
AA or another step program may be another source of inspiration for you. If you’re not religious, go anyway. Find a group you connect with and meet people. Work the steps your own way. If you are a sensitive person, you will be deeply affected by the company you keep. Make sure they are the kind of people that future you that you want to be would want to be around.
The simple answer is “yes”. It is possible. But between now and then there will be a lot of work, a lot of pain, probably even more grief that you’ve stuffed behind a mental door so that you wouldn’t have to feel it. But I think that room might be full and now it’s spilling over.
I don’t know you, so I can’t say if some of what I am expressing is useful for you, or if I’m way off course to what the truth really is. But with the limited amount of information I have, and what I feel about this information, I think that there is a wonderful person who has deep wounds that never healed, and through that came a kind of lashing out in a deep desperation, but that didn’t work and maybe you feel like now you’re just at a bottom of a pit that seems too deep. But yes there is hope. Yes, you can climb out. Yes, you can be happy. Yes, you can love yourself. Yes, you can forgive yourself. All of these possibilities exist for you. Maybe not today or next week. But a year from now? Five years from now? Twenty years from now? It’s all unknown, and the unknown is scary, but the unknown is exactly where all possibility lives.
From here there are so many places you can go. The very best advice I can give you is to watch your thoughts, understand your thoughts, don’t let unconscious thoughts go unnoticed. Learn what negative messages your mind is giving you and figure out how to change them. Your thoughts ultimately create your emotions. Unconscious thoughts create emotions within us that we often don’t understand. We just feel them. Or they can even create emotions that relate back to something that happened long ago that we don’t consciously remember. The point is that your thoughts and your emotions create your actions. Your internal state creates your external state. Positive affirmations are not enough. You need to let yourself feel those things. You need to spend time imagining what you want. See it there, dream about it. Feel what it would feel like to be that person, to have that life. And let yourself feel gratitude for those things, even if they haven’t become a reality in your outside world yet. Gratitude is so powerful. There are parts of your brain that can’t differentiate between the past, the present, and the future. As you take the time to think and feel these things you want, and to be grateful for them as if you already had them, that filters back to your subconscious, which in turn will ideally start feeding you out new thoughts, which will become new emotions, which in turn will elicit new actions from you.
That is my best and finest “random stranger” advice. 
As I said, there is a lot to unpack, so much that could be said. I invite you to come back to this forum, and to come back often. You are going to need a lot of tools in your sobriety toolbox. This forum is at your fingertips whenever you need it. Here you can connect with other people who have similar sobriety goals (no matter how different they might be in other areas). There is a check in thread. Use it daily. The is a gratitude thread. Use that daily too. Allow yourself to connect with other people to the level you feel comfortable doing. This is a public forum, so keep that in mind, but come often enough and participate enough and you unlock the “damn you must really need this forum” level 
Okay that’s not what it’s really called. But it is a locked portion of the forum that is not open to the public. If you feel comfortable enough here at that time, you can be more personal there. Or maybe you’re the type who puts your life on the internet without a thought. That’s okay too.
But this forum is open 24/7, and there are a lot of resources for you to dig through, and there are a lot of amazing people you can turn to for advice if you need. I know at this point I’ve written you a book, but I really hope I’ve been able to reach out and give you something you need to help you on your journey–whether you become a regular here, or if you disappear after this thread fades away.
You can do this. Again, I can’t promise it will be easy. Actually, I’d be more honest if I promised you it will be one of the hardest things you ever do. But you can do it. Yes parts of you are gone, but you are not meant to hold on to every part of yourself forever. You will never be that person you were before, and that’s okay because that means that in the future you will not be the person you are today. You are forever growing and changing, and it really is up to you–through choices you make every single day–who you will become.
I love relaxing in the tub and reading a good book 
