Congratulations on being so fit! I think the first thing you should look at is the foods you are eating. Gas producing food and carbonated beverages expand the intestines. Also, there could be hidden lactose in somethings you are eating.
There are several sites on the 'net that list foods that cause bloating. Here's one that will give you a starting point: http://www.mayoclinic.com/health/gas-and-gas-pains/DG00014
Also, you might want to keep a food diary for a few weeks. Write down everything you eat at each meal or snack, and then note whether you are having bloating. You might discover a culprit food or drink. Lastly, since we aren't doctors, I suggest you discuss the problem with your physician.
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