Abdominal pain can be due to many conditions: gastritis, peptic ulcer, gallbladder stones, intestinal infection, ileus, kidney stones etc. All those diagnostic procedures you've been through have excluded possible organic reasons for the pain. After three abdominal surgeries, however, there is a possibility of experiencing peritoneal adhesions. Pain occurs when parts of the intestines stuck in those adhesions. They can be seen on a CT-scan and laparoscopy, if necessary. If there is no organic lesion present, the only possibility left is irritable bowel syndrome (IBS). IBS is a functional disorder that can manifest with various digestive symptoms including abdominal pain. You can ask an expert opinion from an internist and seek further advice on diagnostics and diagnosis techniques.