Almost seven years ago, I was arrested in college for disturbing the peace.  The incident was related to mushroom use.  Back then, I smoked quite a bit of marijuana as well.  More than six years have passed.  I haven't touched an illicit drug and I have a great resume for the coast guard.  Needless to say, my life changed dramatically since I got in trouble.  Getting in trouble was actually a good thing for direction in my life. 
 
As of recent, I have been granted an expungement on the above arrest record.  Basically, on the Homeland Security backround check form, I can legally say I have never been arrested.  However, there is a question that asks if I have ever used drugs in the last seven years.  It hasn't been quite seven years since I last smoked marijuana; it has been more like 6.   
 
I am applying for officers candidate school in a few months. What would you suggest I say?  Be honest?  If I am, have you ever heard of officers in the Coast Guard or Navy admiting to usage and being accepted?  Thanks so much. 

You will be required to state to the folks at MEPS that you have been arrested even if it were explunged. The military treats explunged records as if they haven't been explunged.

They offer waivers for drug use and just be honest.

Eric

If you were arrested, you were fingerprinted, and those prints were eventually sent to FBI repository along with your arrest record.  Those are never expunged.  Even though a court may expunge the record, a background check for clearance always includes a records check with the FBI.  The arrest will show up.  Not a good idea to answer no, however, you can elaborate on the SF 86 that the charges were eventually dismissed.  If you know the court docket number and/or the name/address of the court that expunged it, that will certainly help to list that on the SF 86.

yes

at age 16 i was convicted of underage drinking. does this ruin my chances of not getting into the Coast Guard?