Maybe you could try talking about what you said here, that you feel immense pressure to come up with a topic and you're uncomfortable wanting things or talking about yourself? That seems like fertile therapy ground right there.

What happens in your sessions after the "I don't know"? How does one of you eventually start the conversation? Or do you just sit there forever?

I'm pretty comfortable with my T at this point. If I'm in a good mood, I'll usually start the session by making a joke or a comment about something and then quickly transition into what's on my mind after that. If I'm not in a good mood, I'll usually sit down silently and my T will put on her Empathy Eyes™ and either ask how I'm doing or comment that I look sad/upset/etc.