Struggling along

[VisceralFlame]

Lately I've been falling behind in schoolwork. School has been a cakewalk up until about this sophomore year. For some reason, I'm comprehending things less easily, and I tend to space out and avoid work. It bothers me. Especially considering I've been told I was brilliant my whole life (gifted program, etc.)
There's also the feeling I'm not completely honest with myself.
Some things I've considered to have caused this:

1. I was diagnosed with ADHD at 6, This might explain the spacing out, and disinterest. Not that I don't love being ADHD most of the time
2. I also feel being a teen might be working against me.
3. Lately I've gained a lot of personal freedom in terms of video games, and they have been a crutch before.
4. One of my classes, Latin II, is causing me much stress because the teacher who taught me Latin I really didn't teach well. He moved and now I'm taking the course online. I barely know the basics from year 1, so year 2 is completely foreign.
5. I'm not getting enough rest.

My birthday is tomorrow and I figure that it's about time I start reorganizing my life and get back in control mentally. Any suggestions/questions/personal experience?

P.S. It seems worth mentioning that a good friend of mine is going through the same thing, albeit with a more apathetic attitude. We're pretty much the same in terms of just about everything besides upbringing. SO I figure I'm not the only person who's gone through this.