I have a stutter and physical symptoms as well. When I have to talk on the phone I'm nervous. Sometimes if I have to order food or something I write down what I have to say and that helps. I know life doesn't come with a script and I can't always do that but I don't stutter if I'm reading. I admire you having a job like this you are facing your fears. However there is no shame in finding another job you are more comfortable with. Life is too short to work somewhere you are miserable and nervous all the time. It will be ok OP.