Just a thought here ... I don't know how your T works, but mine believes in using humor in therapy (he wrote his doctoral dissertation on it). I know of at least two times he did something humorous when he felt that I had had "enough". Did it intentionally to lighten the mood, and after I started to laugh - finally - he went back to what he had been saying.

I'm just wondering if your T saw signs in your behavior or demeanor that made him feel you both should back off from the subject temporarily. I dunno - maybe he misread you, and it would have better to go forward?

As far as his facial expression being blank, that happened with me when I told my T something from my childhood that I thought would shock him. He showed no reaction at all - his face was completely expressionless. Not sure why they do that, but there's probably a good reason.

These are just some thoughts - FWIW. As others have said, just tell T how you feel. Your next session should bring out more so you can decide whether to leave, or take a break, or not.