I know it sounds like u knew u have to do it but really have to teach yourself to calm. Look i will tell my situation right now. I m at Police academy right now and i stutter when i talk with when friends etc. But when we have exams and i Stand in front of entire class i teach myself how to calm down. Now look entire class listening to u officers standing there asking u questions and u have to answer imediately because u wont pass. Now take this u would call it high stress situation and stutter will stutter even more right ? I taught myself to calm down a will tell u that this is only time when i dont stutter. I can speak 30 mins without stuttering because im calm and can pace my speaking etc. Just think about this when someone stresses whats more impotant to u ? U or that dude stressing u ? U are the most important person to u and should care about u only. When they stress u take a deep breath count one two in your head look at their eyes and tell them in your head that they wont stress u u are more important and most impotantly take your time and be calm u can do it man