I really miss my ex and want to cry when I think of him.?

I can't understand why I miss him so terribly as he tried to control and manipulate me. He played the part of the caring boyfriend so well that I kept coming back to him.I sometimes feel that it was all a horrible dream, it really feels like it was not real. I left him for other reasons to do with his child but it is really hard to forget him and totally move on. There are so many memories I have of where we used to go together, and I find it really hard to go to those places we used to go. I had this horrible dream the other night about him picking me up and kidnapping me, i think this might be because he used to joke about wanting to do this. Any suggestions would be much appreciated. Many thanks in advance!