Crystalrose,

Usually, dissociation happens because there is some perceived danger and a person does not feel fully safe. So they kind of "check out" and separate their awareness from what is happening in the present. It could be that you haven't developed enough trust in your t yet. Or perhaps you feel afraid of what the therapy work is bringing up in you. It could be fear of feeling your emotions, or fear of memories. Or something about your t or being with him is triggering you. Can you pinpoint why you don't feel safe enough to be fully present? What would make you feel safer?