Hi, haemorrhoids (piles) is the commonest cause for painless bleeding into the stool. Here the bleeding can be intermittent. Another cause is fissure in ano, where there is pain while passing motion with bleeding. Other causes are inflammatory bowel disorders like ulcerative colitis and crohn’s disease can produce similar symptoms. Here the walls of the intestines are swollen. Diverticulitis, infections and tumors of the colon can produce bleeding into the stools. Please follow up with your doctor, a colonoscopy may help to narrow down the cause. Regards.