So, I’m a complete idiot and got into an argument with my ex of 5 years just now. We broke up a little over 2 years ago - the relationship was mentally, emotionally, and physically abusive. They would drink, black out, hit me, choke me, etc. They went missing for 6 hours in Baltimore City due to a blackout and got a dui not too long after that incident. They were manipulate and would beg me to stay every time I tried breaking up with them to the point where I would cave in and stay. In April 2015 I finally got the courage to end it once and for all (at this point we had been engaged for 2 months). They turned all my friends against me and we’re horrible about it. We’ve gone off and on being cordial with one another since the breakup but all ways get into all ways fight eventually over the fact that they still have some of my possessions and refuse to send them - telling me I have to wait when it’s convenient for them. One item is from my best childhood friend who passed away when I was 19. This fight today started because I asked to get my stuff back again. Instead of having a normal conversation it blew up. My anxiety is through the roof and I really feel like I want a drink…I need to stay strong, this evening I will be 4 days sober and I want to keep that going. What can I do to calm my anxiety!
Anything but a drink! Workout, run, call a friend, type really long messages here on the forum (which I do pretty frequently when I feel myself relapsing), go for a drive, a walk. Go to your local rescue and ask if you can socialize some puppies or kittens. (Seriously, this is a thing.) Work on a project. Write furiously in a journal. Color.
Anxiety decreases with time. Always. Create some time for yourself.
I took your advice. I stopped everything I was doing and took a walk in the beautiful sunshine. I repeated to myself over and over not to let him have any type of control over my emotions and that he wasn’t worth the anxiety. It took about 45 minutes but I feel much better and I’m still sober! 
I always like to read! It helps me use my head for something other than stressing out over relapsing lol
Sometimes I like to clean when I’m getting anxious too. On the times I remember to use more appropriate coping skills to deal with life stressful situations. And now you can feel so good about yourself for not letting him get to so much that you would have to reset what you’ve been working hard everyday at not needing to do. Good for you 
You can also call the local police department and get a police escort to retrieve your belongings. I know it sound like there was some distance that separated you.