This obviously will not work for everyone but have you tried weed. It's been a god send for me. But when I don't have any or chose not to have any that day I encounter the same problems. I'll normally take a deep breath before speaking and hope for the best. Or and I hate this part the most, I have no issues speaking when I explain I have a speech impediment so bare with me. I can say this fluently for some reason and then stammer my name out and feel ridiculous. But it helps people understand beforehand.