Thanks for the reply. I was thinking hemorrhoids, but the fact that my tailbone is hurting makes me wonder. I've read that can be caused by tumors. But I did have a CT Scan of that area, so my thinking was that they would have seen that.
I did do a lot of walking yesterday (6 miles). So I was thinking that maybe I caused hemorrhoid swelling that is making my tailbone hurt and my stool thin.
You did the right thing by scheduling for the colonoscopy. That test will show if there is a problem. From what I have read, colon cancer seems to be more in people alot older than you, but its good to check it out anyhow being your grandmother had it.
I would try not to worry too much because it might just be hemmroids, even if you don't feel like you have them - they can be internal hemmroids and that is nothing to be alarmed about.
Good luck..
MO