Hi bittersweet and Welcome!
I have a son that's had ADD all his school years, he is 18 now... he just barely graduated... due to low grades.

He didn't do homework because he didn't ever know there WAS homework (wasn't paying attention when it was assigned)-- didn't study for tests because he never knew when a test was coming up. He's gotten in several car accidents(his fault) and also speeding tickets, can't hold a job for more than a week as his concentration and focus is so low

.... ... why am I telling you all this?? well, because I believe if someone has ADD or ADHD to the extent that medical assistance is needed... it will hugely disrupt their lives in many ways.
It could be so many different things that are going on with you.... like hormones rising and falling(can cause one to snap at others), mild depression (can interrupt sleep and concentration), could even be a thyroid imbalance(can cause all sorts of symptoms)..... if you feel the way you are now is not the way you'd like to be-- I think seeing a professional about it is the best direction.
With young people it's tough as there is so much going on in active young minds. Please seek a professional's advice, they might be of some help if this is getting in the way of your goals. Keep us posted!
Take care,
mandy