I went through the same tests about 5 years ago for the same symptoms and was diagnosed with IBS. Since the doctor found no cause for the problem, he put me on librax with meals. This seemed to help but still didn't identify the problem. Recently I was diagnosed with chemical sensitivity to fragrances, cleaners, pesticides, fertilizers, and FOODS. These food sensitivities did not show up on standard tests. I am still searching for answers but can give you a few suggestions given to me by others who have been diagnosed with this condition. Rotation diets, NAET treatments, a book (EATING RIGHT FOR YOUR BLOOD TYPE),check for candida infection, and Leaky Gut Syndrome. I know I haven't given you an answer but there could be many causes for bloating. These are just a few things to research as you will find that you have to search out the answers for yourself. The doctor who diagnosed me with IBS explained it as what stomach problems are called when nothing shows up on the tests.