My main concern about telling bf before you speak to T is that there will be a lot of pain in telling anyone, including him, and he is not trained or experienced in how to respond to your disclosures, or in how to guide you through a process of great pain, or in how to pace or limit your disclosures so as to keep the pain bearable. In short, he is not your T. T can help you in those areas, and can offer perspective about what to tell bf, and when.

Again, a thread on this topic in the Survivors of Abuse forum would allow those who have experience to share their perspectives.