Brandon,
You might want to browse this link:

http://www.gocoastguard.com/get-the-answers/faq#How hard is it to join?

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

Honestly, the only thing that Meps knows as far as your medical history is what YOU disclose to them.  Granted, you should be upfront and honest about anything major, but if it is something you feel is minor then I would just leave it out.   

Also, don't disclose anything that is not documented! The only reason I say this is because it will delay your entrance into the coast guard - or any military branch for that matter.   

As far as smoking marijuana its okay.  You can still get in.  I disclosed that I had tried marijuana twice in my high school days as experimentation.  It was no big deal.  They just want to make sure that you don't have a problem drug or alcohol abuse and will make you get a "Psychological examination" if they suspect anything, and the psychological exam is a joke.   

yes

Still in high school and unfortunately did some marijuana under peer pressure a dozen or so times 3 to 4 months back will this DQ me from the coast guard?

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.

Nope!!!
Not in the Coast Guard. Most officer's in the Coast Guard have to get a top secret clearance. Were a Law Enforcement Agency as well as a Military Service. Your arrest will come to life, and you if you stated you never utilized a narcotic, and it showed you did, you could be processed for a general discharge immediatly for lying on your enlistment contract (fraudulent enlistment). For a Secret Clearance an official through OPM will contact people you never thought they would contact. 
Hope this sheds some light into the process... But ask a recruiter without giving your name.. He/She will point you in the right direction. If you have other questions go to www.fredsplace.org, or mil.com Coast Guard discussions. There is a recruiter forum there.

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

I would definitely recommend being honest.  Several people I know had "forgotten" to mention something from the past (one as far back as middle school), and it cam e back to bite them.

I have a question along the same lines as you.

I was not completely honest on my information I filled out for my physical examination at MEPS, as far as medications I had taken in the past.  Although, I have every intention of being completely honest when I fill out the information on the EPSQ for security clearance.

Is this going to hurt me?  Also, as far as medical history goes, what can they find out about?  broken bone in 6th grade?  depression medication?

If I am honest about being on medication in the past, can they find out all the details surrounding it?  Say, I was on medication for depression, and I say it was to quit smoking (welbutrin), can that hurt me?

I know this is a lot, but all the feedback I can recieve would be great!

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.