During running my stomach swells up and i cant run cuz of inability to breath normally and cant poop without metamucil for years. what could this be?

Mouth breathing: This is a problem that many runners have. Normally we breath through our nose, but when running, we often mouth breath. When mouth breathing you are gulping air into you stomach which posses through to your intestines. It is hard to burp when running. Breath through your nose when running or stop and burp occasionally. Eat more fruits and veggies. Keep your urine clear like "Wyler's lemonaid

Metamucil efficacy: is consistent with constipation; metamucil binds water helping reduce drying of stool by colon lining (back into blood stream) & making stool more firm, more difficult to pass. Constipation, perhaps more so in upper colon, would also be c/w abdominal selling. During strenuous exertion, running, bowel works to empty (both ends). If constipated, air/fluid in stomach+small intestine cannot pass down.