I had a similar problem, but it was caused by a lung infection/pleurisy (inflammation of the lining of the lungs that was really painful). I was given medication and my x-rays were coming out better, but I was still in pain. Eventually the doctor figured out that I had tightened up the muscles in my back, side, and stomach, probably bracing myself for the pain before. Then, once the other pain stopped, but muscles never relaxed and then they started to hurt. Push on certain areas and it feels like the worst bruise I've ever had. Plus, I have this dull ache and some spasms.
I'm not saying this is defiantly what it is for you guys, but maybe it started out as a gallbladder attack or a stone that passed, but now you have the muscle pain left over. I've been in physical therapy for five weeks and I'm about 50% better (I had a long way to go, so that's much better). It wasn't the lung specialist that caught it for me, it was my regular doctor. Sometimes they are better at catching things than the specialist who is only looking for things in his field.
Just a thought. I really hope you find what the problem is.