Why can't I get over him?

There's this guy that I wen tout with for 2 years and we were best friends for like 6 years before that. Anyway we got in this huge fight because my dad hated him and we broke up. That happened a couple months ago and I can;t stop thinking about him. He says he hates me and never wants to talk to me again, but I can;t stop thinking about him. I made him my everything and now hes gone and I have nothing left. I didn;t think I cared about himt his much but I have a lot going on and I used to go to him for everything, I don;t know why I can;t stop thinking about him. Help!