I don't under stand his actions?

Me and my twin has always been close until this year. I have always been his rock in his life, it like he has this power over me. Im always there for him when he is scared or when he is sad or upset. Latly he has been pushing me away slowly. It's like when I try to talk to him about anything he doesn't want to hear me, and when we're @ school he doesn't even talk to me in the halls. I know he isn't embarred or something cause every one knows that we are twins. So what up with him? He is hurting me more than one ways. I don't get it? Can you help me.