Had a fecal occult bloodbtest come back positive. had a ct scan done and blood test come back normal and a colonoscopy scheduled soon. no noticeable hemorrhoids. are the chances of something serious small, especially at 31?

That occult blood could have come from your mouth all the way down to the anus. If you're not experiencing black or gross red blood in significant amounts, repeated occult blood tests aren't strongly positive and have no gastrointestinal symptoms, at your age I predict no serious GI pathology will be found.

Unless you have history of early onset colon cancer, your risk of colon cancer is remote. The Occult blood test can be positive from any bleeding anywhere from the mouth to anus and also false positive if you had taken anything with enzyme peroxidase, e.g. horseradish.