I used to be that way too with ex-T. I would have a "list", get in there and it was like my mind would go blank or I would minimize my feelings "it's not that bad". I would leave my session mad I didn't talk, ruminate and want to text her. I would write everything I wish I had said and sometimes read it in the next session. I found that once I wrote it and got it off my mind, it helped. But, if I was trying to figure something out, the thoughts could last for days.

My current T. allows email which helps. I usually email her that night with my regrets/thoughts and schedule another session. Those items go first on the list for the next session and she knows to bring them up to help me not clam up. I usually then email her the day before my next session with a list like "fear of spiders". I go in to more detail in my session.

My ex-T. didn't allow contact so it made it a lot more difficult. Of course, the best thing to do is to talk to your T. about it and hopefully she can come up with a plan to help you.