Your lower digestive tract needs to be examined closely. The origin of the hematochezia
is usually as from the large intestine up to your anus. Intestinal infections generally such as salmonellosis, shigella, enterotoxigenic E. coli, worms etc could be held responsible. So a stool exams + culture would be indicated here.
The other non-infectious causes could be anorectal tumor
(likely with advanced age), anal fissure
(not likely as you feel no pain during defecation), internal hemorrhoid
( very like as might be painless and non-protruding). A colposcopy
will be indicated in this situation.
You need to consult a visceral surgeon as soon as possible for prompt diagnosis and management. A visit into an emergency room would be wise of you at this moment.
Hope this helps