I did something to my arm back in March.. 8 months I know. Since then I have not been able to sleep on my right arm unless there is something under me to take weight of it. I have even slept on it wrong three times so badly I couldn't even pick up my arm. It felt like my arm weighed a hundred pounds. It took about thirty seconds all three times before my arm had enough strength to do anything. The pain is in on the backside of my upper arm directionly in the middle. It used to bother me when only doing certain things.. but now it throbs doing nothing. I just can't take it anymore.. anyone know what it may be?