Bad shoulder injury?

im a 15 year old girl and i picked up a shot put and i put my arm up (like when u raise your hand in school) and cuz i put it up and it twisted a lil or something, cuz then my arm fell (it like collapsed)behind my head to the other shoulder and it killed. it hurts right where the bones come together but only in the front. it kills to move it and it pops wen it try to move it alot. please help me it has to be better soon cuz im gonna wrestle. please.
i have hurt my shoulder b4 i dislocated it in july of 04 playing dodgeball