I really relate to this. I sometimes have to go several weeks between sessions, and I keep a list of things I want/need to talk to my T about. But then suddenly, the second I step into her office and she asks "So what do you want to focus on today?" I have NO idea what to talk about. Suddenly all the problems I had been keeping note of seem insignificant.
I'm sorry I'm not of much help or have any advice, but I just wanted you to know you're not alone in this