Colon Cancer 3 years after Colonoscopy

I am 27 year old, 4 years ago I went for a colonoscopy due to bowel problems (cramps, flat stool e.c.t) they found a small adenoma 1mm in size. I went back the next year and no polyps were found. Now 3 years after that I am going for another colonoscopy. I am terrified because my problems have gotten worse. Is it likely that I could have colon cancer 3 years after a clean colonoscopy? How fast do polyps grow? Is it possible one could grow to the point that it is causing flat stool in 3 years? I am very worried any information would be helpful.