Could you talk to your school counselor, like penguinh said? Or another mentor, teacher, church leader, older sibling, even your boss if you're employed? If you really feel like there's no one you can open up to, you could try writing a journal. That helps me sometimes.
If you're in crisis and there's no one to talk to, call 1-800-273-8255. That's the crisis line for the US. They'll be able to talk you through the worst of it. There's also a crisis chat at their website, but it has limited hours whereas the phone number does not.
National Suicide Prevention Lifeline