During the past few months, I have had CHRONIC gas that simply will not go away, along with alternating bowel movements (one extreme to another), and slight bleeding on the surface of rectum. Could any of these be a sign of colon cancer? I am a 34 year old male. I had a colonoscopy in October of 2006 and it showed nothing, could colon cancer have grown that fast (less than three years)? I have read that it's an extremely slow-growing type of cancer.