Bleeding after stools that is not associated with pain is usually caused by hemorrhoids. Of course there are two types (external and internal hemorrhoids). I am assuming that has been excluded by your doctor and the negative scope results.
How about your coagulation profile? Family history of colon polyps? Medication history. I checked your medical history but unfortunately, there's not much written there.
How long has this been going? You do not have fever? Is the bright red in color?
Other causes include inflammatory bowel disease. Obviously you're concerned about cancer. Assuming that you do not have a family or personal history of colorectal polyps or cancer, and no other symptoms, your risk is small. We are more concerned about those above the age 50. All of this should have been excluded with the colonoscopy.
Please keep us updated.
Dr. Tamer Fouad, MD
MB, BCh, MSc Internal Medicine.
Consultant of Hematology - Oncology.