Hi. Thanks for your query. Noted the history and understood your concerns. Loose yellow stools and abdominal pains for such a long time of couple of months should be investigated and well evaluated clinically. Since ultrasonography and colonoscopy are normal the cause may be in the small intestines. Hence you need further evaluation and investigations of CT scan of the abdomen. Tests of stool for three consecutive days. Tests of blood including that for sugar, thyroid and liver functions. A course of an antibiotic, metronidazole. Activated charcoal and probiotics. Multivitamins, particularly therapeutic dosages of Vitamin A and D. If any specific diagnosis is made during the investigations, get it promptly treated. If all the investigations are normal, then get treated for IBS that is irritable bowel syndrome.