I still have feelings for my ex bf?

He was so nice to me and i had to move so we broke up but we still talk on facebook but i miss him alot.He liked everything i did..... the outside,videogames, everything. I just cant let him go. Many of other boys have asked me out and i said no to them because i cant let him go. I think he still likes me though,but im not really sure.But he is so nice he moved on and has had plenty of girlfriends but i just cant seem to move on.and i know this sounds weird from an 13 year old, but it is true.Why is that?