It's okay.
It's okay to let go of people who are a negative presence in your life. It's okay to remove yourself from a bad situation. We've all had to do it. Sometimes it's a friend. Sometimes it's a significant other. And sometimes, sadly, it's a family member. Whoever the person, whatever the situation, in the end you will be better off distancing yourself from the source of what/who is hurting you.
Yes, it is going to be hard and sometimes seem downright impossible, but you can do it. Some people need to go the journey alone, and others need the support of friends and/or family to help them tough it out. Whichever way is best for you, do it.
Find things that make you happy- truly happy- and do them. Get out of the part of your head that is over analyzing the bad stuff, and focus on things that improve your life and well being. Do something different; do something active - go on a hike, take a roadtrip, seclude yourself in the mountains with no cell service, make a beach trip, devote time to community service (because sometimes helping other is the best way to help yourself).
I'm not saying distracting yourself is going to fix your problems, and I'm not saying run away from your problems. I'm saying everyone heals differently, and everyone finds their peace in different ways. Nobody should (and the right people won't) judge you for getting out of something that is destroying you.
Take back control of your life and remember:
You are more than the bad situation you have kept yourself in.
Your are more than the negative way he/she makes you feel about yourself.