You'll be fine. I passed a military drug test when I thought I wanted to join the navy. I was in roughly the same situation as you. Then again that was like the one time I've smoked in years. I decided against the military when the recruiter suggested testing for steroids.
Just drink a lot of water, I drank/drink 5 gallons a day, and try to get some cardio in. Especially fasted cardio, as the break down of fat will carry out THC in your urine and sweat.