inexplicably miserable today

well it's not. I could explain it, but the explanation is "I'm tired and lonely and want to do things with other people, but doing things with other people is hard because I'm tired, they're tired, and the world is shit"

but that's not a satisfying explanation!

I guess nothing is satisfying really, but that's the depression talking

God I hope it's depression. I really genuinely hope there is something wrong with me

I don't want this to be normal. or worse.

that explanation is 100% valid! i'm sorry you're feeling miserable though. hopefully things start looking up a little for you