I have pain in my lower left abdomen which spreads to lower left back. alread had appendix out. also have diarrhea and ribbon like stool. what is this?

See a doctor: This could be a meckel's diverticulum, diverticullitis, colitis, or half a dozen or more possibilities. Go get seen, examined, tested, diagnosed and treated. Hope you are better soon.

Several issues: Diverticulitis colon cancer colitis needs evaluation and likely colonoscopy.

See a proctologist!: You may need to be examined well inclusive a colonoscopy/sigmoidoscopy. It can be diverticulitis. Of course a stool examination as well, good luck!