You note a sore right side as well as having to take 8-10 Immodium tablets per day (assume for chronic diarrhea).
Inflammatory bowel disease, irritable bowel or infectious causes leading to colitis are all possibilities. I would suggest a CT scan first to evaluate the possibility of inflammation of the bowel wall. The CT scan can also evaluate any masses which may be present.
If negative, a colonoscopy would certainly be a reasonable test to further evaluate your symptoms.
Radiation can also lead to inflammation of the bowel wall leading to diarrhea. Again, the colonoscopy should be able to detect if this is indeed the case.
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.