My past is ruining my current relationship, what do i do?

His behavior is not normal and it's not you that has the problem. I'm a guy and I don't exactly k now what it's like to be in your shoes but from my perspective it seems that you're investing more into this relationship than he is. If he's going to keep the relationship open and not fully commit to you then you have to wonder if it's worth being with him when there's certainly someone better out there.