I agree with Surgeon in his comments that gall bladder or pancreas are certainly possibilities. Other causes can include an ulcer, inflammation of the stomach or esophagus, or GERD.
Tests to evaluate this would be blood tests (to evaluate the pancreas), an abdominal ultrasound (to evaluate the gall bladder), or upper GI series/upper endoscopy (to evaluate the stomach, esophagus and small bowel for any inflammation or ulcers).
Followup with your personal physician is essential.
This answer is not intended as and does not substitute for medical advice - the information presented is for patient education only. Please see your personal physician for further evaluation of your individual case.
Thanks,
Kevin, M.D.
Happy holidays,
Kevin, M.D.