Pylori, Hypochlorhydria, gastritis, candida infection, parasite
or other bad bacteria. It can happen from picking up a parasite
while travelling, genetics, or just having a poor diet as some have suggested above. Ultimately, the intestinal system from the esophagus to the anus is not working appropriately, because if it were, the gas and bowel movements would be "normal". Traditional medical doctors do not necessarily do the tests that find the problem.