It sounds like you are addicted to the drama. Sometimes when relationships are that rocky the excitement becomes more addictive then the actual relationship. The true test would be if the relationship was that appealing when the drama ends and it's just you and him. I think the fact that he cheats creates this feeling of I want to have him (but if he fools around on the side and it is exciting). If number one has your heart than you don't want to spend your life with number two. That makes no sense. Why spend your life with someone you settled for. You have to decide what you want. Your behavior can be very hurtful. Decide what you want and go for it. If you don't want the guy that wants you leave him alone completely.
If this has been helpful press accept