Bloating feeling under right ribcage when sitting. not painful, no nausea, just discomfort. doc thinks possible gallbladder? could it be liver?

Unlikely: If your doctor has done tests to consider gallbladder disease, he or she has likely already done blood tests to utilize the liver function and/or an ultrasound of the gallbladder which also would look at the liver. If these are normal, it is unlikely that your symptoms are due to liver disease. If your symptoms persist, follow up with your doctor who suspects the gallbladder. Good luck.