Hello, With reference to your query regarding stomach ache which you noticed about 4 days back in the upper part of stomach has moved down to lower stomach and very tender and also had diarrhea. Stomach pain whether you noticed in the upper part and moved down to lower part could be due to Gall stones, Pancreatitis, GERD, Lactose intolerance, medication side effects (like non steroidal anti inflammatory drugs), diuretics, glucose intolerance, endometriosis, thyroid problems, parasites (Giardia and cryptosporidium), appendicitis, ulcers (peptic or stomach or duodenum), stress, too much sugarless gum, food poisoning, inflammatory bowel disease, Irritable bowel syndrome, cancer. Having these causes in mind, you can do complete blood count, liver enzymes, urine analysis, pancreatic enzymes, plain X-ray of the abdomen, ultrasound, MRI, Barium X-rays, CT Scan, Endoscopy, Colonoscopy are the investigations to be done depending on the cause and severity of the pain and arrive at a probable diagnosis and treatment can be started immediately. Abdomen is such a large area where you cannot pinpoint on one disease, a proper history, physical examination, and laboratory findings all together leads to a probable diagnosis and treatment follows through. I would suggest you to consult your physician for the same. Thank you.