Pain in the left rib that comes and goes and seems to b in different places , can it be gas or something more serious?

Costochondritis: Fleeting rib pains are often caused by a vague condition called costo-chondritis. It is a mild degree inflammation of rib cartilage that may be more annoying than serious. You can try OTC anti-inlammatory agent like Ibuprofen 400 mg 2-3 times daily for week and use heating pads to the area. If pain subsides, it weould suppor tthis diagnosis. If not, pl. get it checked by your local doctor:)