I need to let go...

I've been the side chick for over 2 years now. I know I need to end things with him but my emotions get in the way. I've cut all contact with him 3 times and he's always showed up on my door step with in days of cutting him off. I really do love him but I know we will never be together and if we were he'd cheat on me too. I suffer from bipolar/depression and abandonment issues so that makes it even harder to stay away from him. I feel the only way to totally get over him is to move away but I don't want to leave my family behind to do it. I don't have any friends to talk to so I really don't have a support system to help me get through it till I'm emotionally stable and able to move on with my life. I just don't know how to let go. I don't need criticized, I need encouragement and support.