Anybody know what this could be?

I am a cheerleader and when I was lifting up a girl who weighs ninety something pounds (I only weigh 113) and I was the backspot. She started falling and when I caught her, she fell on my shoulder and all her weight was on it. She was about 6 feet in the air. Well I couldn't lift my shoulder straight up so I went to get an X-ray. It wasn't broken or fractured, but the doctors don't know what's wrong with it. Whenever you lift it up in a certain position it pops, but my wrist and 4 fingers are double jointed on that arm so idk if it's that or something is wrong with it. It's been 4 days and it's still pretty sore. Does anybody know what could be wrong with it?