As the other folks have said, colonoscopies are not bad. I've had a bunch, since colon cancer also runs in my family. They are good to do, because if by any chance you do have it, it's best to catch it early.
Both of my relatives who had it just had surgery to remove the cancer and surrounding intestine, and they were fine.
For your own piece of mind, please just bite the bullet, so to speak, and get checked out. Okay?