Why do I bleed after I poop? But its not painful.

Intermal Hemorrhoids. Rectal bleeding is a serious concern. Depending on your age, the two major surgical concerns are internal hemorrhoids and possibly malignancy. Other factors matter, i.e. - dark red v bright red bleedings, bleeding noticed on paper v blood with the stool. Either way - a visit to your doctor is needed.
Maybe hemorrhoids. Bright red blood typically from anal or rectal problems. Internal hemorrhoids typically bleed and are painless. Other possibilites also, some are serious. Get checked by yrour doc.