Instead of asking why you HAVE to say all the details, why not ask why you don't WANT to say all the details. It seems as if you are afraid of getting too specific because then maybe you will feel it too much and re-experience the pain. Maybe your trying to avoid it so you can avoid the questions and getting into it. What she doesn't know won't come up, right? I think it might be your way of avoiding dealing with this pain. She is there to help you, and experiencing and talking about the pain is what therapy is all about. No, you have HAVE to say the details, but if you are holding back anything important, its kinda a waste. think about it.