Absolutely, you are allowed to write down your troubles on a piece of paper and give it to the school counselor to read. It's essential for you to feel comfortable and find a way to communicate that works best for you, especially if you have social anxiety.
Many school counselors are understanding and experienced in dealing with various communication preferences and challenges. Providing a written note can be an excellent way for you to express your thoughts and feelings without the pressure of speaking directly, and it can help the counselor better understand your concerns.
When you meet with the counselor, you can hand them the note at the beginning of the session, and they will likely take the time to read it and then discuss your concerns with you. This approach allows you to share what's bothering you without feeling overwhelmed by speaking about it directly.
Remember, the school counselor is there to support you and help you navigate through your challenges. They are trained to listen non-judgmentally and provide guidance. If you have any other specific requests or accommodations that would make you feel more at ease during the session, don't hesitate to share them with the counselor. They will likely be receptive to finding ways to make the experience as comfortable as possible for you.