I am experiencing a change in my bowel movement. They have become increasingly stringy. The tend to stick to the sides of the toilet bowel. Today I had a bowel movement that was pretty dark. I have been watching for blood in bowel movement but I have not detected any, though the dark color of the one I passed today could indicate blood. Are there any other possible explanations for these symptoms beside colon cancer? I have a colonoscopy on Tuesday. I just want to prepare myself for possible bad news.