Tightness in the stomach after period w/ bloating. Am constipated & have cramps. Had sharp pains under left side of ribs. What could this be?

Gas buildup. Abdominal discomfort in the left upper quadrant with bloating is often due to trapped gas in the splenic flexure of the colon. Applying a hot water bottle to the abdomen helps break down the gas and enables you to pass it. A gentle laxative combined with a stool softener like senokot (senna) also should help you.