You do seem a little depressed. Yet you would say that as recently as a year ago you had a lot going for you. You're blowing things out of proportion if you take this one bad year and try to project it over your whole life as if the bad year predicts the rest of your years. Your history actually shows that not long ago you had it going pretty well.
I was faster junior year than senior year. Injuries were part of it. Actually, having a girlfriend also slowed me down as I focused less on running, so consider that for a minute!
Girlfriend dumped me at the end of senior year.
I didn't run in college.
Now I'm with a totally different woman, have run plenty as an adult, and my PRs were all set after high school and after college. I don't say this to pat myself on the back, but to point out that you're being pretty unfair with yourself. Running is a sport that builds on your previous training. You can easily improve by keeping at it for many years to come, even if you sometimes regress before improving. You were naïve to think the girlfriend you had would be the best lady for you. How many women have you actually talked to with any interest in your short years alive? Not many. Odds are you'll find an even more appropriate fit of a woman by getting older and meeting more of them along the way.
Getting good grades may not be fun, but this isn't about the grades per se. It's about your level of involvement in your daily life that includes going to school every day. It just sounds like you're checking out a bit. Don't do that to yourself. Live in the moment or you'll keep thinking life stinks, because you're never experiencing it when it's right in front of you. Make the most of what you're doing right now, even if it's school. You'll only ever live in the present.