My lower left side (abdomen) hurts when i fart/try to fart and when i sit down. what is wrong?

Possible dicerticuli: First of all don't shoot the moon in a work up. A flat plate of the abdomen and a physical exam including a rectal exam would be in order. If no sign of constipation etc then see your GI provider for a scheduled colonoscopy. The colonoscopy should be delayed if there is fever, increase white count and localized peritoneal signs. Treat with ab, then when cooled down have the colonoscopy.