arm, shoulder, shoulder blade

I hope you can help me, I have been so worried about what I feel on a daily basis.  I have severe pain in my left shoulder blade,the pit of my left arm, and in my upper left chest muscle vey close to my arm pit (sometimes with tingling here).  It ALL radiates down my left arm with very severe pain.  the burning and tingling drive me bonkers.  Of course my first thought is that there were problems with my heart, however my doctor assures me there is nothing to worry about.  His next comment is fibromyalgia, very frustrating to say the least.  I am hoping you can give me some pointers as to what to stretch, what kind of doctor I need to see, whatever you think might help.  After reading your posts I can see it in my mind the two muscles working against each other.