What is up with this guy?

At first he is nice, we have a lot in common, but he has a huge ego. He is so vain and once you compliment him once, he brags or asks why, for example . me: your handsome . him : yea and why's that? -__- and etc. He seems to talk to me whenever he feels like it or when hes bored. But yet when he talks to me, he seems so charming. He even seemed to have liked me because when he does talk to me, it gets interesting, and has wanted to hang out with me and etc. Suddenly when i revealed that i used to like him, he didn't seem to mind, or use it as an excuse not to talk to me anymore. After he tells me I'm a real nice person to talk to and etc. he insults me by saying i should go lose some weight days later.... Now hes suddenly talking to me again 2 weeks later... what the hell is up with this guy?? Why is he acting like this? I really like him as a friend, but why does he act so coincided and cocky towards me ?