No it's not okay. Mid teens to early twenties is the time manic/depression and schizophrenia set in. You need medication.
You don't know you're schizo if you are. Extremely depressed could indicate bi-polar. Your parents would be angry to know you are self-destructive and you are too young to diagnose yourself.
I went through every single one of the things you're talking about from 7th grade through high school with the same people. I never cut. Stress is something you are going to have to deal with your whole life. Get use to it and find other ways to cope. Take Karate. Take art. express yourself in different ways. And no, if you have schizoprenia your family and friends may chalk it up to "she's unhappy." Same thing with bi-polar. We have both in our family and it's not something people want to acknowledge. So I know what I'm talking about. Your family doesn't hate you, they don't understand your feelsing. People care about you, but you're pushing them away whether you know it or not. Write to your best friend. If the people who turned on you were real friends they would be standing by you. These are all normal things everyone goes through. You're no different.