Thanks for taking the time to open up.
Anyone is susceptible to vicarious trauma, more so professionals/first responders etc because they are regularly involved in traumatic situations. From what you're describing, it really does sound like that's what you're experiencing.
I know with things like this it can feel as though you're the exception, and you start to invalidate your own experiences by comparing it to others (ie. someone else has it worse, so I'm doing fine). I'm glad you've reached out on here hopefully to accept within yourself that you are in fact experiencing vicarious trauma, compassion fatigue, and poor mental health from being a support system for so many people.
It's a lot of pressure for one person. I can see that you're a really good friend for being that support for so many. But it's important to know that you need to set boundaries between yourself and others when you're in that position, and put your mental health first. It isn't selfish, it is completely necessary to your health.
You've mentioned that you find it really difficult to share your feelings. It sounds like you're bottling a lot of things up to the point where you can't function for days at a time. You're exhausted, angry, tired, and it sounds like you're experiencing a lot of anxiety. Everyone is relying on you to be their support network, and it sounds like you don't have that for yourself, and you're feeling really burnt out emotionally.
Have you ever considered reaching out to a GP for a mental health care plan, or taking the steps to talk to a professional? How would you feel about taking the steps to do that?
I want you to know that I hear you, and your feelings and experience is valid, and it's so important for you to take care of yourself. You aren't equipped to deal with ptsd, and as you've said, you're only a kid.
How do you think your friends would take it if you were honest about how you were feeling?