You sound as though you never got any closure from the relationship, you never got any answers or an explanation, so in your head nothing makes sense for why it ended, which is why you can't let go. All I can say is, in time you will get over it, It may take a while, I have missed someone for a year and a half before I felt as though I could really genuinely learn to love someone else. That is really the only option you have, to just wait it out, because you can't ask him for closure or an explanation now. You've already come so far, four months is a long time, to talk to him again would just make it hurt more. So get out there, distract yourself, perve on hot guys, flirt with them, improve yourself, and before you know it you'll think of his name and not miss him anymore.