Stuttering only when knowing the text beforehand

Stuttering only when knowing the text beforehand Hi! I block almost exclusively in these situations: * Talking to people who interrupt me often * Making "official" phone calls where I know what to say * Raising a hand and waiting to ask a question in class * Telling a story or a joke i.e. only when I have time to mentally "rehearse" at least once and it's not spontaneous speech anymore. Does anyone have this type of stutter? Any tips?