Why does my brother act in these ways?what the hell is he trying to do to me or prove?

The very fact that he says complementary things about you to your mother shows that he is attached to you. The reason why he behaves like what he does may be due to an inferiority complex on his part, particularly because of ur good health and physique. After all, he is ur brother; do not take his behaviour seriously but keep your mother informed about your discomfiture with a request that she should advise him. Don't get excited or annoyed but take things in its stride because of the close relationship. Be as normal as possible whenever u meet him, since u both meet only four times in a year.