I don't see your age, even on your profile. Might be your gallbladder.
it could be a problem with your kidney, it sounds like the right area for it. you could have a kidney stone, which would cause blockage and will usually back up your system. you should get a ct scan of the area and see if anything comes up. do not let your dr send you for an ultrasound, as its not common for kidney stones to show up on one. many drs think they will, and occasionally they will, but it doesnt happen often. my family has a history of stones and theyve never showed up on an ultrasound, so get a ct scan to check.