Thank you for sharing, I totally understand and know what that feels like. I have a bad stammer which causes me to block of any word I want to say when I'm feeling nervous.

I get nervous anticipating any form of public speaking outside of a small group people that I feel comfortable with.

Fortunately, my team mostly uses slack for intra department communication but slack can't be used for everything. The worst for me are round table meetings where participation is mandatory, i.e going around and taking turns to introduce yourself, or conference calls with new people.