Hi. Pain in abdomen for one month is a long time to suffer. I would recommend you to consult a Gastroenterologist and get an upper GI Endoscopy done. As also to undergo the relevant tests of blood to rule out diabetes, liver function and kidney function tests / Urine and stool tests- particularly for occult blood in stool. Ultrasonography of the abdomen and CT scan if necessary will be required to get the proper diagnosis and not to miss anything. The probable causes can be related to cholecystitis, gastric Ulcer or Cancer, Pancreatitis, liver pathology and so on. All these aspects will be covered by the above tests to come to proper conclusion to get you the perfect management plan- whether medical or surgical.