multiple stool tests, colonoscopy, biopsies

My husband has been having the same abdominal pain for about 3 months now. It is centralized in this lower abdomin right next to his left hip. We have gone to a gastroneurologist- they did multiple stool tests, colonoscopy, biopsies- which all came back normal. The dr. then asked us to seek attention from a family practioner, which we have and the exam for hernia and other male issues and stool tests have come back negative/normal. When going to the ER the CT scan, urine tests, and blood tests were all normal. Everyone seems to be stumped. What else could this pain be? I was told by a friend that their grandfather went months to dr.'s and they finally figured out that they needed to graph the muscle. How would that be found if this is what was needed? I am tired of going to the dr. every 2 weeks to be told that there is still nothing they can come up with or that all tests are clear. What else should we be looking for?