Bad back pain & strong left side stomach pain goes toward middle too. hurts to breath normally. usually have a lot of gas. sligh fever ?

Pain: Sounds like some sort of infection as you have a fever. On your left side/abdomen the most common infection or issue for someone your age is either a kidney issue like pyelonephritis or a stone or if pain is lower down is some ovarian process. Less likely for your age is diverticulitis. I would go in for an exam to help determine cause and proper treatment.