Have u ever gone to an al anon meeting? i just started but i feel they are helping me already. Your ex has to want to change. you can't control him and u didn't cause his behavior and u cannot cure his behavior. Right now it might be helpful for you to focus on yourself.
also in regards to romantic relationships- we tend to get into relationships that mimic our relationships that we're comfortable in, which are the ones we had with our parents. That is why they are so hard to let go of. I am trying to work through some of this stuff myself too.