Hello, I understand your concern. It does seem unlikely that you have developed lactose intolerance, since the effects of a lactose diet would be almost immediate. There is however a very simple way to rule this out by completely avoiding intake of milk or milk products for 48 hours. If your symptoms stop, then you are definitely not lactose intolerant. The complaints you are experiencing could be due to celiac disease or irritable bowel syndrome. In this case, a blood test (to check for anemia and other abnormalities), as well as a test for tissue damage or inflammation would be the next reasonable step to diagnosing your condition. Wishing you good health and all the best.