It sounds like a typical case of cholecystitis, however pancreatitis has to be ruled out as well.
These are 2 conditions where both Amylase and Lipase levels are elevated, however, cholecystitis affects the upper right quadrant.
The lack of a diagnosis, should this suspicion prove to be correct, puzzles me, as it is rather common and simple to diagnose. I guess, there's always the possibility of missing what seems to be the obvious to most doctors.
If your gastroenterologist is not willing to be supportive and work with you, perhaps, seeking a 2nd opinion would be the logical next step. Ask for a HIDA scan which has high sensitivity, if the ultrasound does not help in establishing a diagnosis.
BTW, diabetes is a risk factor in both cholecystitis and pancreatitis.