under my right rib cage, I feel like someone is tugging on my muscle. I feel like the muscle is trying to roll over. I can sometimes literally feel that muscle tighten up, and spasm.

I spent years thinking I had a gallbladder issue (had it removed) or having some sort of liver or intestinal issue. (ct scans, mri's and so forth reveal nothing) the only explanation was when I was dx with MS, and someone explained the "hug" to me. I thought it would affect both sides, but for me its only one sided. The MD said it was common to be one side of the other.

If I rest when I feel it coming on, and or use a heat pad, or a TENS unit, and stretch to help it, I can prevent the full on painful yanking sensation that can start if I dont head it off. It can be painful.