What Causes Pain And Discomfort In The Left Arm?

for a couple of years now, I have had a very mild, but building discomfort in my left arm. it almost feels like a nerve pain that either radiates between the elbow and ring/pinky fingers or sometimes up to my shoulder. it changes all the time. more recently, I ve been feeling a similar discomfort in my armpit area, or even shoulder. on occasion the feeling is not there, but I can t tell if it s simply because I m distracted and not thinking about it. at the same time, my left leg has had similar discomfort. moving back and forth from knee to hip - mostly on the back of my leg. and I noticed that when I exercise and get sore muscles, my left side becomes A LOT more sore than my right (which would typically not be unusual since it s my weaker side) but it seems more extreme than it should. of course I read online about conditions that could result in this and I see/fear the worst case. cancer and whatnot (pancoast region of lungs). I ve talked to three doctors about it (all family doctors) but none have given much direction on what to look for. please offer some suggestions if you can. thanks! janine