Please help!! Why is my ex so mean?

I dated my ex a few years ago, fell in love with him, blah blah blah. He broke up with me years ago and I still don't know why to this day. I've had a bad life and he's my best friend, so I enjoy talking to him, but he treats me like crap a lot of the time. The sucky part is that I still have feelings for him. We argue almost constantly, and for periods of time he ignores me and then will talk to me a few days later. He always makes fun of me with anyone he talks to at school, and I never talk to him at school because I don't want to embarr him. He always asks me who my boyfriends are, if I've been having , etc. He also views my Myspace profile a lot. (I have a tracker, but they're expensive.. They do exist. He doesn't know I have one though.) Anyway, what's his problem..? Does anyone have any clue why he may act like this, and why? And what should I do about it? I'm tired of being ignored and him making fun of me, then apologizing and talking to me as if nothing ever happens. I hate it.. I want to be his friend, but I've told him how I feel, and I don't think he gets it.. I don't think he realizes I'm really tired of it. He has this idea where he thinks I'm "wrapped around his finger," and it's somewhat true, but I want to be strong enough to prove him wrong. Please give me any advice if you can!!