I’m glad you are seeing a therapist soon. Your issues are beyond what I can responsibly respond to in an advice column. I can tell you that what you are describing is not usual in a 14-year-old. I think you are right to be concerned and that seeing a therapist for an evaluation is absolutely the right thing to do.
You wrote an excellent and articulate list of symptoms. I can tell that you’ve been doing some research. I hope you are sharing your concerns with your parents. Ideally, you will have their support while you try to get to the bottom of this.
Some of your symptoms (speech issues, hallucinations, memory problems) suggest that maybe there is a medical issue. While you wait for the therapy appointment, I suggest that you see your physician for a physical check up. Take your list with you to that appointment. If there isn’t an underlying medical problem, knowing that will give you peace of mind. If there is a medical issue, you can start some treatment to get some relief.
I also urge you to take your letter to the therapist. It will help you ease into a first session. It will also help the therapist know where to start.
I wish you well.