Could i have cancer at 26 yo? constipation and a little bright bleeding off/on for about a year or less. blood is mostly there when constipated.

Unlikely!: Cancer is uncommon in young people but it is not impossible. So let us get you checked by a doctor to find out the cause of rectal bleeding. it may be an anal problem due to constipation but that would be only an assumption. A physical examination is essential to check that part of your anatomy, and may be, some tests, but a doctor's check up is advised.