I'm having an existential crisis at 14
What makes you think you're having an existential crisis at that age?
I don't understand why people make a big deal about everything in life.
Adults have a lot of issues that 14 year-olds don't. And the reverse is equally true. That's why kids and parents sometimes have a hard time understanding each other.
I think I'm going to ask my teacher about it tomorrow.  Do you think I should go talk to them?
Talking to your teacher to better understand is a great idea. They can help clarify some of the behavior you might be seeing.