Bright red blood when having a bowel movement may be due to hemoorrhoids.
Hemorrhoids develop over time due to chronic constipation (passing hard and infrequent stools, straining to pass one).
Additional symptoms of constipation are abdominal pains like cramps located especially at the lower abdomen and feeling of abdominal bloating.
These symptoms of abdominal pain, constipation, bleeding, fever, may indicate a presence of diverticula (a small bulging sacs pushing outward from the colon wall) in colon.
Colon polyps need to be taken into consideration, too.

Best wishes!
Marija