What happened to my neck? I cant move it.?

I was with a couple friends on a trampoline and I slipped and i fell head first pretty hard and fast on my head and now i cant move it at all. I cant move up and down or side to side and i cant even look anywhere, i can only look with my eyes. The doctor said most neck accidents happen on the tramp and stuff and I was wondering what happened to my neck? did i sprain it? help plz!! (ow)