To Spiderman 476
It definitely sounds like you have intercostal neuralgia. I had the exact same symptoms for a while - also thought it might have something to do with the heart but couldn't quite pinpoint the pain - somewhere above my left breast, under my arm.. I went to my brilliant GP yesterday who diagnosed me with intercostal neuralgia. Particularly if you can't pinpoint exactly where the pain is coming from, this is indicative of nerve pain. He recommended a good chiropractor and if that doesn't help, quatersone injections offer relief.