I woke up one morning to a steady pounding on the right side of my rib cage, just under my armpit . Thump, thump, thump. Every few seconds. Like a heart beat. It didn't hurt, but it was noticeable. A spasm. Constant. Every few seconds. I tried to feel it with my hand, to tell if my body was actually moving. I had my son put his hand on my side. He felt it.