Hello, disneybug, Excessive gas in the intestines come from two major sources. We swallow air everytime we eat or drink. The second is the fermentation process that takes place during digestion. Especially carbohydrates or starches produce more gas. Lentils, Beans (like Garbanzo, Kidney etc) can cause more gas. Some people will have bacteria in excess in the small intestine producing more gas, condition is called Small Bowel Bacterial Overgrowth . People who are smokers also swallow more air. I am glad you are trying to quit, plese do. People who chew gum a lot, can have more gas. Gums containing fructose or sorbitol can have more gas. Lactose Intolerance is a major cause of excess gas. You need a breath test to find out if you have this, unless you can avoid all lactose containing products and see if there is improvement. Celiac disease can cause malabsorption and cause you to have excess gas. You need special blood tests to rule this out. Excess gas build up can cause back pain from pressure on the nerve endings. The pain may be totally unrelated and may be like a pinched nerve due to Sciatica, from strain or sprian. Hope this will help you to discuss the problem if it persists with your doctor. Wish you well.