Another possibility could be IBS (irritable bowel syndrome) or fructose malabsorption (fructose can cause pain and bloating if it is not being absorbed properly). I agree you should see a doctor, but ask if they can test you for any of the suggestions listed here. A lot of people seem to find the Atkins Diet beneficial which cuts out carbohydrates – possibly the Paleo Diet could work as well, because it cuts out grains (although maybe do some research into this). In the meantime, visit your chemist and ask for a good quality probiotic to help build up the good bacteria in your stomach.