Did u ever find out what was causing this pain? I have the same exact pain.
Since the ultrasound was okay, I'd think endoscopy would be next. I've had colonoscopy and it was not bad at all. My older sister recently had upper and lower endoscopy, and she was all stressed out about it, but she did great with her tests also.
My symptoms were similar to yours and turned out to be gallstones, but I expect they looked at your gallbladder when they did the ultrasound you mentioned.