HI. Your history of pain in abdomen with diarrhea, abdominal swelling, increasing after food on the left side under the left rib cage is suggestive of following things: -Colitis of the left colon _Gastric ulcer / Cancer -Pancreatitis. as the most probable cause. I would suggest you to undergo the investigations first to find out the cause properly to facilitate proper treatment ::: Blood- complete blood picture, kidney functions tests, blood sugar fasting and post-lunch, Urine- routine,microscopy, culture and sensitivity ( before start of antibiotic) Stool- routine, microscopy, occult blood Ultrasonography of abdomen. CT scan of the abdomen Colonoscopy Upper GI Endoscopy All these test will give us the diagnosis to decide the proper and curative treatment.