Why does my arm hurt when i play baseball?

So i joined my schools baseball team and we are just practicing right now. First we stretch then do warm up throws and stuff. My arm (elbow area) starts hurting a little bit when we are doing the warm up throws but then when we are batting off the tee and in the cages, my arm starts to hurt a lot!! It goes away after several hours after practice and the next day i feel fine, until i go to practice again. Its the same scenario everyday. Does anybody know why this is happening or what i should do?