Well, first there nothing "wrong" with you. There are a few actions you have or haven't done that are helping lead to this issue, but there's nothing "wrong" with you in particular.

That said, guys are oddly possessive. Once they have something, they get bored with it and want something else. Once that thing is gone though, they want it back.

From another man's perspective, he's playing a cruel game with your emotions and I really hate the old "we were friends before ..." blah, blah. It's not that he's intentionally trying to hurt you, but it's that possessiveness rearing up in him.

It's going to be really hard, but you need to be able to separate yourself from this situation until you get your feet under you. Tell him you two can't be in contact until you're able to get yourself in a good, stable situation and that it's healthier for the both of you.

But remember, there's nothing wrong with you, it's just a tough situation.