I know your struggle my friend, all too well. This is very hard advice, because it's very difficult, but you just have to stop caring so much. Trust me, it took me about a decade to stop giving a shit, but I'm there now and it's much better. You probably don't notice it, but LOTS of people have weird idiosyncrasies with their speech. Some lisp, some slur, some spit a lot... most folks have something. Don't beat yourself up! The best thing you said is that you feel at ease and block less when you feel more important than someone. Try to get in that mindset more because it obviously is helping. You ARE important. Don't get inside your own head and defeat yourself! You can do it dude. Take a deep breath, be confident, and if you do block who gives a shit? Try again.