I have a yellow mucus stool, and when i wipe its also yellow. i am 16 years old and worried i have somethinglife threatening/cancer whatisacommoncaus?

Proctitis?: Cancer doesn't cause this sort of thing, and cancer is exceedingly unlikely at your age. Maybe an anal fissure or abscess. Perhaps proctitis (rectal inflammation) due to inflammatory bowel disease i.e. Crohn's disease or ulcerative colitis. If sexually active involving your rectum, STDs (gonorrhea, chlamydia, herpes) are possible. All possibilities are potentially serious; see a doctor soon.