I had that, too... for YEARS! I still don't know if it was my gallbladder, liver or colon (you can absolutely feel colon spasms up there).
I tried an experiment with my pains: I followed this diet: http://www.gallbladderattack.com/gallbladderdiet.shtml
and tried the Beet Recipe at the bottom. After literally two days, the pains stopped. I made the beet concoction every time the pain flared up... maybe three more times... and every time it went away in a day or two. After that, it stopped entirely. I haven't felt it in a couple of years now.
That said, in the meantime, I've also gotten some control over my anxiety, I'm exercising more, drinking more water and I've gone on PPIs for acid reflux, so I have no idea if it was the diet/beet mixture or the other stuff that cured the pain.