IBS vs. Lactose Into. Is it a particular food or simply dairy? Maybe it is something more serious than simple ibs or lactose intolerance or even food allergy. See your pcp immediately for referral to the correct specialist. Try an elimination diet in the meantime. Avoid dairy for a week. If no help, then eliminate other foods one at a time.
See your doctor. There several possibilies for what is causing your problem with cramping and diarrhea immediately after eating. Irritable bowel syndrome is probably the most likely, but other problems such as food allergy or gluten sensitive enteropathy should be ruled out.