Hi, I was knocked down hard on my right shoulder now 3 weeks ago while playing football since then I cant throw a football, extend my right arm or press off of my right arm (ex. pushing myself off the ground). When I do any of those things near the lower middle of my shoulder I get extreme pain and it feels lower middle shoulder expands and someone is ripping it apart. The pain only occurs when I do those things and when I stop those doing one of those three actions the pain instantly stops. The day of the injury and the two days after I could not move my arm or pick anything up. Could anyone please tell me what is wrong and tell me what I should do.