Why does my friend put me down all the time?

I would have a talk with him about this, tell him he is hurting your feelings, and you feel like if he is a good friend he wouldn't be doing these things to you. I also think he is wanting attention from others, which he is probably getting, but it is not the attention he thinks he is getting, believe me they notice how he is treating you and they are not thinking he is a cool person. You may tell him as much when you talk to him. Tell him if you wasn't his friend, and he was hanging out with someone else he was treating this way , that they wouldn't put up with his trash!