For 15 Months, Every Bowel Movement After Sitting In Toilet

for 15 months, every bowel movement after sitting in toilet water for 5-10 minutes, has blood around it. It - the red colour stays at the bottom of the bowl right around the stool. waht is it? can it be cancer? I have been to dr. had a good result from colonoscopy. I fear it is some kind of cancer other than colon. My dr is puzzled but not concerned.