You really got to push past your block. Is it fear? Not being present in the moment? I would try to figure out what it is that isn't allowing you to communicate and work on that.

For me, lately, the "I don't know" comes from exhaustion and not veing able to process things well in the moment. But I don't have an issue going in the next week and telling my T what I wanted to/forgot to say.

If you're just going to update/fill her in on things you didn't say...just do it. There's nothing to fear.

If the information is "sensitive" like you feel like she's going to judge you, then write it up, print it, and bring it in. And push yourself to read it to her. Therapy takes effort. Push yourself a little. You'll feel better when you do.