What does it mean when you bleed from your butt hole?

At your age. Its may be a hemmorroids, or tear in the skin called a fissure. As you age it could point to colon cancer and if you have a strong family hx it's not impossible at your age though very rare. Try to reduce constipation by using MiraLAX (polyethylene glycol) and go in if it's heavy, i may be missing something. Gd luck.