Oh boy do I have good news for you - nobody is looking at you if you're not currently talking, and nobody is going to notice or care if you look down or have the "minutest reaction".

People are primarily looking at the speaker, secondarily at themselves, third is probably checking slack/email/whatever and only in a deep 4th or 5th place is anyone paying any attention to the expression on other people's faces.

Realizing that nobody is paying that much attention and doesn't care hopefully can make the calls less stressful and exhausting for you.