There can be several reasons. Any type of upper GI condition can lead to this - ulcers, GERD, motility disorders, gall bladder disease. Reaction to the various medications mentioned can lead to nausea.
After several surgeries, there is a risk of bowel obstruction, which can also lead to nausea.
You can consider an upper GI series or upper endoscopy to evaluate for the various upper GI conditions mentioned above.
A CT scan can help evaluate for bowel obstruction.
These options can be discussed with your personal physician or in consultation with a GI physician.
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.
Kevin, M.D.
Medical Weblog:
kevinmd_b