Why do I still have feelings for my ex?

I'm 16, and he was my first (and so far only) boyfriend. We were friends for 3 years and dated for 7 months (only light kissing, no or making out or anything), and I had to break up with him near the end of the school year because of all that was going on at the time. I didn't cry when we broke up, and we agreed to stay good friends. He and I are complete opposites, yet we seem to really understand eachother when talking. Well he has spent most of his summer at his sister's place in WI. He came back to town yesterday, planning on staying for a couple days, and stopped by my house before visiting anyone else. He had just found out that his dad got a job in Kuwait of all places, so he is going to have to stay with his sister for the rest of high school. He told me he missed me while he was in WI and gave me the most depressing goodbye hug ever before he Ieft. I've never given much of a crap about boys, but he was just special. He understands me (usually), listens to me, and actually cares about me. I feel really dumb asking this question, but I just need to know why I still like him this much! Please don't tell me to move on, I'm honestly giving it my best effort.