Hey, kudos on changing your life! And sorry to hear about your marriage.
First things first. Sobriety will have to be the cornerstone of your new fundament, with a clear mind and no escaping from reality you will be able to learn more about yourself, find out what the life you actually want to lead looks like, feel your boundaries, what gives you pleasure and hope and what is healthy for you. You can then set to work building that other life for you and your kids. Bit by bit. One day at a time, as we say in recovery.
Just abstaining from drinking isn’t enough as I can tell you know cos you’ve already joined a gym so that’s amazing! I’ll attach a few links to get you started and find your places around the Forum.
Resources for Recovery
Here are some resources. Pick a few. Give them an honest try. Mix and match further down the line if things aren’t up your alley. There’s so much help out there. Just find what’s right for you.
Your #1 tip for sobriety (over 2 years sober)
Some wisdom from ppl who’ve walked the walk before you.
Checking in daily to maintain focus #53
Our daily check-in is super active. You’ll make friends and be cheered on in your journey.
Gym selfies, weightlifting & fitness 
Join us in the gym. We all know how good it feels.
Best of luck to you. Welcome here. You are not alone.