I told my T about "that look" once when she was giving it to me. I think it is her heavy thinking look. When I told her, her expression changed at once and she rolled her eyes at herself and said, "Yes, I know that about myself. I do that." and we both laughed.
Now when that look appears I tell her. "You're giving me That Look again!" Sometimes we laugh and other times she doesn't let my statement turn into a diversion or tension breaker if we need to stay focused and if the tension is a good tension can push me past a place of comfort and to some self discovery.

Our history of learning and of experiences makes us think that T might react like others have reacted. But this is different. He is inviting you to be open. It sounds like he's encouraging you but not wanting to pressure you. You get to set the pace in therapy. He is encouraging you and letting you know it's okay. He might have to do this many times and for a while before you can trust it. And you might trust it in very small doses, or you may trust it one time and not the next. That's okay. It's part of the process.