Enlisting in the Navy and Drug use?

I want to enlist in the military. I have a college degree applied to OCS but did not get in. I have one concern. On my OCS app I divulged medical issues such as broken bones. Only problem is I admitted marijuana use while in college. It has been three years since I last used it, never bought or sold, never arrested, I used it less than 10 times. If I never admitted it I would just lie, but I am sure that my application is on a database somewhere. I would like to know if I have worry about waivers and job placement.