Pinched Nerve

Hey Doc, I have been to 8 specialists, none of whom can help me, please give me some direction.

About 3 years ago I started going to the gym to lift weights. I was going about 4-5 days a week and started to really take shape. However, around about the 4th week I started to feel this sharp pain under my left arm. There was no pain when I was lifting the weights, or immediatley after, it felt as if the bigger my arm got the more painful and tight my arm got. When I say tight, I am referring to whatever it is under your left arm that is attached to the arm pit and runs down your arm. It feels alot larger and tighter (like piano wire) compared to the one in my right arm. It is most painful when i pull down on the skin under my left arm.

At the moment there is no pain because the pain dissappears when I stop lifting weights (Arm gets smaller?) This is driving me insane because all my friends are working out and I have not been able to for years. Everytime I do start lifting weights again, after about 3-4 weeks the pain and tightness returns. Please help!!!!!!!!!