Thank you for writing JustAnswer with your health question.
If this is bright red blood is usually coming from the rectum or end colon. Darker blood will come from higher up in the intestine, and dark tarry blood comes from the stomach or esophagus.
The most common reason for bright red blood in the stool is from either hemmorroids or fissures. Fissures are little tears in the lining of the rectum or colon that usually occur from pressure due to constipation, which is also the cause for hemmorroids.
Some people can also have ulcers in the rectum or colon. This can be due to different disorders, a common one is called ulcerative colitis.
If you are on antibiotics sometimes a severe reaction can cause bleeding.
You will need to go to a health care provider to find the cause, whether, hemmoroid, fissure, ulcer, or other conditions such as a diverticulum, polyp or cancerous growth.
Let me know, if this is bright red blood, how much bleeding is occurring, so that I can direct you as what to do about this until you can be seen by a health care provider.