I can not tolorate harsh laxitives in prep for Colonoscopy?

19 years ago I had a gallstone stuck in small intestine and lost small portion of intestine as result. When I went to get Colonoscopy prep recently, I could not tolorate the magnesium citrate and rectum started bleeding & was raw for days. Cancelled Colonoscopy, but have family history of colon cancer, so need a test I can tolorate. What is one as laxitives are too harsh? I can't even eat tomatos or spicy food, let alone harsh laxitives. What can I do for a test other than Colonoscopy?