I think what’s going on is that you trying to manage three different emotional issues at once. Your letter shows you to be an exceptionally emotionally aware person. You are going through the physical changes that happen in adolescence. And, on top of that, you mention kind of as an aside that you have been diagnosed with PTSD. Any one of those could make a person shut down (or at least try to) when overwhelmed by emotional situations.
The teen years can be tough because so much is going on. You are figuring out who you are. Your body is changing. You are trying to figure out who you will love and what that love stuff is all about anyway. If that weren’t enough, you have apparently been traumatized by some event or events that were so severe that you developed PTSD in response.
I hope that having a diagnosis means that you are also being treated by a mental health professional, preferably someone who specializes in trauma and adolescence. You don’t have to figure everything out on your own. In fact, it’s not even wise to try. A professional can help you manage the effects of trauma and sort out your feelings.
Medication is not likely to be helpful for PTSD for someone who is only 13. No medications have been approved by the US Food and Drug Administration for the treatment of PTSD in children. What you need is talk therapy. Trauma focused cognitive behavior therapy has been found to be the most effective. You need a mental health counselor who has those skills.
The best help I can offer you is to encourage you to make an appointment right away to someone who can hear your whole story and who can provide you with regular and consistent support and advice.
If you are already seeing a counselor, do take your letter and this response to your next appointment. It may help to direct what you talk about next.
I wish you well.