What Causes Abdominal Pain With History Of Appendectomy?

I v had an emergency appendectomy 22 years ago, I had pancreatitis and gull stones, and had my gull bladder removed about 5 years ago. I ve had pain at 8 on a scale 1-10 for two weeks. Blood work good, ultra sound good, CT scan negative. I went to a gastrentrologist and a general surgeon and they are stumped. The pain subsides when I lay down on my back. When I sit, stand or walk to the pain gets extremely bad in my upper right abdomen. What could it be?