I can provide some general information on this topic.
In the United States and many other countries, therapists are bound by professional ethics and legal obligations to maintain client confidentiality. This means that they are generally not allowed to disclose information shared by their clients, including information about underage drinking, without the client's consent.
However, there are exceptions to this rule. Therapists are required to break confidentiality if they believe there is a serious risk of harm to the client or others. This might include situations involving child abuse, imminent danger to oneself or others, or instances where the therapist is legally compelled to report certain information, such as suspected abuse or neglect.
Laws and regulations regarding confidentiality can vary by jurisdiction, so it's essential to understand the rules specific to your location. If you have concerns about confidentiality, it's best to discuss them directly with your therapist, who can provide you with information about their confidentiality policies and legal obligations. Remember that therapists are there to help and support you, and open communication about your concerns is crucial to building a trusting therapeutic relationship.