It would be good to talk to your guidance counselor at school about this. If you can talk about this with your parents, that would be good. There's a number of reasons why you may be having these problems and so a good check-up would be a nice start. Sometimes, being females, we get hormonal changes that effect the way we feel and as a teenager, it can be even worse. Whatever the case, you do need to talk to someone. Keep posting!
"If you watch the stars at night,
And you find them shining equally bright,
You might've seen Jesus
And not have known what you saw...
But you would notice a gem
In a five & dime store."
From-"Mary Was An Only Child" by Art Garfunkel