Your therapist is the person in the best position to help you. He or she knows you well and can provide the support and guidance you need. But a therapist only has what you share to go on. You are depriving yourself of your therapist’s best efforts by withholding such important information.
Please put your embarrassment aside. Consider showing your letter and this response to your therapist as a way to ease into the conversation. A therapist’s job is not to judge but to help. My guess is that, once you open up, pieces of the puzzle of your distress will immediately start to fall into place. It’s very possible that the conversation will begin a new and important chapter in your healing.
I wish you well.