Had 4 ct scans spread over 3 years, diverticulosis dx, rigid sigmoid to 35 cm, no evidence of cancer, but sympotomatic 3 years, cancer??

No Ca: At your age there is always an association of diverticular disease and Ca. The old motto is "if you leave the cancer alone it will grow on you" holds. After 3 years with no signs of progression of symptoms one would expect that any complaint is diverticular in origin. If it still persists, a rigid scope is not adequate which is why colonoscopy should then be considered.

Unlikely to be Cancer: Cancer in the Colon is uncommon under 40 years of age. So you should not worry about it. You have already had too much done to you. CT scan is not a good test for Colon Cancer. So I would not have done it one time, yet you have had it 4 times! What symptoms do you have? We can help you to control your symptoms now that you have had all this testing.