Option 40 and SF-86 question, please help?

Ok so I enlisted into the army and got an option 40 when I was 17. I went into the 14 month DEP. I didnt lie at meps when I went down about drugs, I really hadnt done any but two months later I tried marijuana like twice. I didnt find it worth it and I never did it again. This was about a year ago now. To be a ranger you have to have a secret clearance, which means ill have to fill out the SF-86. Im not going to lie on this form, its not worth it. I dont want to live my military career with a lie over my head. Anyway, will admitting to this deny my clearance? Like I said it was only twice about a year ago. I just dont want them to think I lied at MEPs and get a fraudulent enlistment or something like that and I dont want to be kicked out of the military or lose my Option 40. I know a friend of mine in the military who had a friend totally lie about doing drugs then they found out he did do them and all they did was deny his clearance and he was stuck in AIT for I think 6 months.Anyway, what do you all think will happen? I go to basic in a couple months. Any help would be very much appreciated.Thanks!