16 year old male with blood in his stool

Hello.  my 16 year old son has been having bright red blood in his stool periodically for the last three years.  When he first told me I took him directly to his doctor when he preformed a rectal exam. The blood is in the stool & he does not have hemmeroids. My son was sent for a colonoscopy, which was normal. Why would he still be having this? He is not constipated & has regular BM's.  He is starting to get worried about this & so am I.  Should we investigate further?

Thank you.
Trish

[JeffMitchell]

If it's bright red blood then that is new blood. It would have to be coming from the lower colon or rectum.

Sounds like hemmeroids to me. I'd get a second opinion.