The right thing to do is come completely clean. Its bad enough to be isolated at this time and left to your own stinking thinking without the proper guidance, but even worse to not come completely clean to start fresh. Such a halfway measure will come back to bite you, and while I understand you are afraid of even more stuff coming down on you, it will be far worse when your deception come to light.
You really do need a trusted adult who knows what they are doing and I encourage you if you are afraid of the cop, to confide in your drug awareness counsellor to remedy this situation with the additional pill. Of course you can't see the dangers of still having a stash, (a substantial one?) and risking the cops thinking you are a seller, because all those people you turned in will surely tell them how much and how long they have been supplying you to save their own skins.
You don't know how many times I have seen this happen, or how many time I have seen people fresh from being caught, or beaten up by their addiction, and want to clean up, be tempted yet again to use just a little bit, because they have survived the initial storm and feel better.
If you are serious about changing your life, then don't expect good results to come from half stepping and stinking thinking. Let me be clear. The same things that got you in this mess is still there, waiting bite you in the butt really hard. I wish you had a trusted KNOWLEDGEABLE adult for guidance and support. That goes for your dad too!
http://www.na.org/