I was seated and all of a sudden I had a pulling, not excruciatingly painful but painful sensation of a muscle in my left armpit being pulled/spreading up into my left chest below my collar bone (the pain could be reproduced by pushing on the surface of my chest and on my armpit).. I also had a little numbness in left arm and most of my symptoms went away within 5 minutes. I rotated my shoulder and stretched but the weird thing was the pulling that started when I wasn t even moving my arm. The symptoms have subsided but is this a heart attack? I had a stress test last year and was fine. I ve had this happen a few times, with no rhyme or reason and do not know what it is. It happens so infrequently that I ve forgotten to tell my doctor about it. Should I go to the ER?