Today I started having a sharp, horrible burning pain under my left arm on top of my ribs, close to my breast, but not in the breast. I felt the pain this morning, but then not all day until this evening. I was taking a shower and the pain hit me suddenly and so hard I almost cried. It's been coming and going for the past hour now, depending on if I raise my arm, breath in deeply...or whatever. I didn't physically injure myself in any way. Anyone have any idea what this could be?

It's not heart burn. It's not in my chest at all. It's on the left side of my torso, toward the top, but not quite to the armpit.