It might be a good idea also to get some blood work done and get checked for H.Pylori, Celiac and Ulcerative Colitis and Crohns. Hope any of this helps!
Have you tried getting a Cat Scan done? That might show you more. I'm at a loss. I don't know what it is. If you had said it was just on the right side or even towards the middle, I would have thought appendix. Could you possibly have an obstruction? Even if you were only partially blocked and things were still getting through, it could still cause pain. That happened to me. I'd ask for the Cat Scan next and maybe an Upper GI with lower bowel follow through. That could show any blockage or ulcers (if theyre big enough) or Gerd or Acid Reflux. An Endoscopy is another idea. You did say you got an ultrasound done, right? So we know it's not the gallbladder. Gosh, I just don't know what to tell you!
Sorry I can't really help. I honestly don't know what could be going on with you. I'd keep going back and insisting on more tests, though. You know your body and you know you're in pain. Keep pushing until you get your answers. Best wishes to you.