It helped me and my T a lot at the beginning of my therapy when I would e-mail him what was going on IN THE MOMENT that I was struggling. He couldn't help me right then, but he could at least see what I went through. For me, going to session and being with T would sort of automatically make me feel better (or maybe more numb?), and I couldn't quite access all of the fear and angst and flashbacks and whatnot that I had to deal with during all of the hours I wasn't in session. Even if you can't e-mail (I don't know what your Ts rules are), you could journal and bring with you.
Over time, as I felt more safe with T, those feelings started coming up more in session and he was able to help me as I worked through them. I'm kind of back to the "shut down when with T" place right now, but I know as I feel more safe, I'll be able to access that stuff in session again.
I hope you feel better