Tightening under left rib cage. doc thinks ibs or twisted colon. taking meta musal. now having burning gas.

Doubt it: If you feel full/tight in this area it is often trapped gas in what is the highest point of your intestines when standing. Lay down with your butt above trunk level & the gas should eventually pass. Your colon in that location is tied to its location & does not twist. IBS is a vague label that has many subtle symptoms & could also be present.

Not simple answer: The differential diagnosis for that complaint is long, so those kinds of specific diagnoses can only be made by doing specialized testing. Suggest you go see a Gastrenterologist to sort out the real possibilities before you wind up having a bunch of expensive tests done with no definitive answer and treatment solution...