Can you be a pilot after being diagnosed with Generalized Anxiety Disorder?
The first thing is to determine if you were evaluated for anxiety, or diagnosed with an anxiety disorder.  Your primary physician's office can answer that because it will be in their records.

Often (not necessarily applicable in your case) symptoms which do not require ongoing therapy or medication may not have hard diagnosis.  

Avoid assuming that you have a disqualifying condition.  Contact your physician and ask if you have that diagnosis.  It might help to explain why you are asking, specifically that you would like to fly and get an FAA Medical, so that they know the context of the question.

You might also want to read this FAA writeup on Item 47:

https://www.faa.gov/about/office_org/headquarters_offices/avs/offices/aam/ame/guide/app_process/exam_tech/item47/et/

As a final note, as an instructor I have had several students over the years who had serious, diagnosed psychiatric issues.  Most of them got effective help. A few became ineligible for a FAA medical. One refused to seek treatment as they were concerned about losing their medical. (I discontinued providing instruction, which aggravated the problem.) However, I know of no pilot or pilot wanna-be who had to take a class on anxiety or anger management, or personal relations, or similar to be denied an FAA medical on that basis alone.

In your case, the anxiety may have been situational, and developmental (as an adolescent) and clarifying whether you have a diagnosis (as opposed to just an evaluation) before you spend the big bucks for an AME exam would be appropriate.