Well, you know? Everyone has a bottle that they keep clamped shut, and I can tell you that having that bottle released with someone to lend a comforting hand is the most amazing feeling in the world.
True, everyone has different situations but there really shouldn't be such thing as 'better' or 'worse' situation because everyone deserves the same respect.
You're not whining for attention, you're genuinely seeking out someone to talk to. :) And we are all here for you.

*grabs knife*
Let's put a smile on that face

Calm down, Jeff the Killer.

You can talk, I'm close to your age so I'd understand.

Well I just said everything that was on my mind

Look, you aren't being edgy. You are just a teenager is all. Bottling up emotions doesn't work if you have no outlet. What makes you angry or sad?

Today I felt sad, either because of school being school or because I admitted this to you guys, and I burst into tears.
And I get angry pretty easily for no reason.
Maybe it's just hormonal imbalances and mood swings?

Hormones are like an atomic bomb on your neurons&co.: during puberty your brain is intensely reshaped! You get rid of 40+% of your pre-puberty synapses, especially in the area which controls your behavior (I'm simpifying a lot, ok?), and the circuitry is not considered mature until your early 20s!
Now, in your teenage years, you're supposed to explore your limits (new experiences: smoking, drinking, romance), to find out what and who you like ("I'm really into Maths", "Jay is definitely my BBF"), to form your own opinion on things ("Death penalty is absurd")... You're trying to gain independence, so that you can find out who you really are.
So I'd say that mood swings are pretty normal and so are feelings of inadequacy...
Some of these issues continue afterwards, I won't lie, but you get to control them more easily.

Try not to worry (too much), you’re NOT alone, ok? DON’T YOU EVER think that you are being weak for expressing your doubts, your fears, whatever. Some idiots may believe it, but A) you’re being brave B) you’re being intelligent C) you’re being mature. Being able to recognize your feelings is a rare ability, it helps a lot and it is useful for the future, so practise it. Maybe you can talk about how you feel with your parents, who you might think are very old and ranty individuals, but – guess what? – they have experienced the same unease as you do now. Give them a chance! Unfortunately, some parents don’t make you feel comfortable at all, so you can go to another adult (I sound like “WikiHow”, great! ‘-_-), like uncles, aunts, cousins, grandparents, teachers you like, trainers, etc… Of course you can also get advice from friends you trust. And from us, obviously! We will try not to let you down.

That was really well explained, daek knightess. Banana, don't be ashamed, this is normal. You can always come to us for help. I'm even ok with ranting.

My problem is that I can't complain to my family because everyone's always like:
"God's given us a lot and we're very lucky and we could be worse off" and, while that's all well and good, there's no reason why someone can't feel bad. That's like saying Bill Gates physically can't frown because of all the money he has.
It makes no sense how I can't say that I'm displeased with my life because then people think I'm being ungrateful.
One should be able to be unhappy but not ungrateful, and to say that he shouldn't is a gross lie that I will never believe.

So I guess you guys are all I got. It's not that I don't care for you guys; it's just that I'd rather have someone in real life actually fucking listen to me instead of threaten to take away my laptop or my Xbox or my phone.

Oh sheesh, bringing religion into it. Then you can't say anything. I agree with you, happiness is relative. What exactly are the problems?

I just said it.
I feel like I can't feel sorry for myself or else I'm being ungrateful.
And I can't complain to my family or else I'm being ungrateful.
So basically I'm expected to be happy 24/7 or else I'm the antagonist.

Last year, I had friends in real life. This year, all 9 of them ditched me. The only person I can talk to is my little sis, and she's 11. I guess we're the best you can get.

Alright, you can be sorry for yourself. No one should be forced to be happy all of the time. All you can do is fake happiness, or do your best to get a friend to talk to.

Recently I've been very pissed off because in my eyes this is pretty much the worst time in history to be born.
We have people like Donald Trump and Hillary Clinton, both of whom came dangerously close to the White House and one made it inside.
We have people that ditch us for no good reason.
And I'm starting to seriously consider that I might be a little more than just "sad". Maybe it's hormones. Hopefully it's hormones.
I just hate everything. I even noticed in my PE class that I didn't know it was possible for me to hate so many people around me at once. School sucks, my family sucks, life sucks and I hate it all.

I suppose it's better than being born with the plague around. The problem now is how society is. Very fake, everyone is fake. I hate nearly everyone at school, they're all so basic and stupid.

They all just...do the same thing. It's like a hive mind or a server room.
They don't listen to reason. They don't get good grades. They all act for the clique instead of for themselves.

They don't give a shit about the world, all they care about is finding cheap romance with one another. And starbucks.