Stomach discomfort feels like it's under the left rib and sometimes small amounts of mucus in bowel movements and occasionally constipation.

Irritable bowel : This is fairly classic symptoms of irritable bowel which is a nuisance. If your symptoms have been stable for some time i would see a doctor for workup. You can get something called splenic flexure syndrome where there's a gas bubble in the place where the colon kinks up by the spleen in the upper left abdomen. I don't see it too often.