Had rectal bleeding for a few weeks 2.5 years ago. No bleeding since. Dr said it was likely fissure that healed. Would colon cancer continue to bleed?

Rectal bleeding. If your rectal bleeding has come back, then okay to get in to your doc for evaluation. More likely this is a hemorrhoid or recurrent fissure. Cancer in your age group is very low incidence. However, an exam under anesthesia will lead to a diagnosis, and treatment. Good luck.
Colon cancer. Given your age and symptoms your doctor is probably correct. If you are not bleeding and not having symptoms i would not refer you for colonoscopy to evaluate for colon cancer. And yes, colon cancer would continue to bleed and would have caused multiple other symptoms by now.