I stutter sooo much, and I worked a commission only retail job for 4 years. For some reason when you are put in the situation and are forced to talk, it starts coming out and you will learn the right words to use. I still struggle with my insecurity, but I know it's mostly in my head. People don't seem to care and if anything it allowed me to really build up confidence, I was promoted to sales manager and was killing it. Don't worry about what people think. Just do you. Know that there will always be assholes, and you are probably way smarter then them so fuck em.