How do you get over it when they're all you think about?

I can’t seem to get over my most recently ended relationship, He’s not your average person, He not, He gains a sort of control over you, I’ve never felt so strongly about someone. I have been dealing with this feeling for over a year and I’m sort of concerned, We broke up for like a year, Literally, and got back together not too long ago but he treated me horribly towards the end and I couldn’t take it any more, Then a few other things that I won’t get into but the reason for him treating my the way he was is because he had already moved on while we were still together. My question is not how do I get him back but how do I get over him when a day doesn’t go by that I don’ think about him, The thought of being with someone else in any way makes me sick to stomach. I just want to be able to move on like he has.