I'm 14, in 8th grade, and I am always so fucking tired. I am constantly sleeping in class (every class except PE, everyday). I've been being so tired all the time that I completely forgot how it feels to be wide awake. Like my tiredness (if that's even a word) barely changes from when I first wake up to when I'm in school during the middle of the day.

I sleep 8-9 hours a night, so I don't think I need more sleep. I've tried drinking energy drinks and coffee, but they have almost no effect on me and I don't crash at all, whereas all my other classmates go berserk after drinking just one can. I've looked it up online and people said that it has to do with caffeine and sugar intake, but I usually never eat candy and drink water most of the time.

Is this part of puberty or something? Does this happen to anyone else?

Have you noticed yourself being a bit feverish, and/or has your appetite changed at all? Sleepiness like this is a sign of Mono, which is getting more common these days in kids your age.

You probably don't have it; it may just be a phase that comes with puberty for you. However, it's still good to look into. The only way to tell for sure is by getting a blood test, unfortunately.

A sore throat is also another sign, so if you've had a lot of that lately... yeah.

I feel completely normal (other than the fact that I'm tired) and I never lose my appetite. My throat started hurting yesterday, but went away this morning, and that was the first sore throat I've had in a while. I'm pretty sure it's not mono.

In that case, I would say to just try to wake yourself up first thing. 5/6AM, get up, take a shower, and try to be awake. If that doesn't work, take a cold shower (torture, I know). You might want to just take a day to sleep in. Drink plenty of water and eat closer to your bed time.

Go to a doctor

Or take B-12. It's a natural vitamin tablet that helps you stay more awake in the morning. It's a lot healthier and cheaper than energy drinks.

Just a couple minutes ago I started feeling really light headed and dizzy. I thought it might be that I'm hungry so I went and ate some stuff, but it didn't go away. It's slowly going away right now though. I've been doing some research, and one of the possible things I might have is low blood pressure, but I doubt it because I read the causes, and I don't have that high of a heart rate. One thing I am concerned about is that when I sit/lie down, then stand up I get dizzy for a couple seconds, and this happens pretty often, like around once or twice a day.

Ever think it could be narcolepsy?
My mother has this and for years doctors couldn't figure out what was wrong. There are medications for this, but over the years my mother has fought this where she no longer needs them..in any case you should go to a doctor(or..a neurologist) and ask them to check if you have a neurological disease like narcolepsy.
Hope this helps (:

As for the dizzy-ness, Could it be vertigo? Or maybe you need glasses? loss in vision could do this to you, or if something messed with your equilibrium..which in my opinion is worse.
I use to have the dizzyness, where you feel like you are swimming on land, not fun.
Go see a doctor, please!