Im suprised with cramping on the right side that they would just do a sigmoidoscopy. If I were you, I would discuss doing a colonoscopy instead. If your going to have them half way through your colon, might as well have them go all the way. Could find that its Chrons.
I am 31. Recently I also have indigestion problem for 5 months now. They have done Ultrasound, endoscopy, and CT Scan but didn't find anything. I have scheduled for sigmoidoscopy.
-Davis
What kind of checkup did they do? How old are you? Could be anything IBD related. Diverticulitis, Ulcerative Colitis. Its on your right side, so perhaps Chrons. Even hemorrhoids. However, blood in stool, especially that much can be an issue. You can become anemic, and it could also be an indicator of bigger things. I would recommend booking an appointment with a GI doctor. They will determine if a colonoscopy is needed or not. Keep us updated, and good luck.