This is NOT your fault. period.

I went through a horrible HORRIBLE breakup with a girl who cheated on me, manipulated me, and tore me down into thinking it was all me. I too had no closure, and I can tell you now that looking back, I learned a lot about myself and relationships.

I know you may not want to hear this, but the BEST thing you can do (and i really do know how impossible it seems) is to grieve your loss. You cannot and must not be with this person again, ever. You will not. This person is gone to you. He has destroyed any respect, trust, and care that a relationship needs for a basis of survival. run the course of emotions that feel natural. maybe write a letter to him explaining how you feel, and why you know you must never be with him again, but don't send it. this is for you. he more than likely has disassociated himself with the entire dilemma at this point, and would care less about your feelings right now. But its you that need not care.

I think you are aware that he is not the person for you, and that there is someone way better out there for you. Go get a new haircut, and maybe a new outfit. make some positive changes to help ease your mind and mark this as a point of no return.

As far as the bipolar thing, it sounds like he may have bipolar disorder, but acting in a horrible manner is not necessarily an effect of bipolar nor the other way around.

This guy will not change. i can almost guarantee it. the person he is dating will soon realize this, and he will most likely create the same scenario he has with you.

How long has it been? how old are you? Do you have a close friend or family member you can talk to about all of this?