I'm a former chronic stutterer who largely doesn't anymore and certainly never worries about public speaking even when I occasionally do. I see poor self confidence as a byproduct of stuttering not a primary cause. The vast majority of my experiences with speech therapy, aka the people who studied their whole lives, was toxic in the extreme producing nothing but an increased frequency of stuttering. Whilst I am on record as having used certain drugs to lessen my anxiety around stuttering short term I have also made it clear that for me the cure was always to return to the mechanics of speech and learn how to make the sounds I had failed to understand proiduction of as a very young child. For me speech therapists whose primary methods of treatment centre around confidence are either misguided fools or charlatans who spread little but misery. You can take what you want from this but I am someone who at 25 couldn't say may own name and now since my late 20s I talk to groups all day everyday as part of my living. I have survived stuttering in to adulthood, come out the other side and in speech terms am flying. The only speech therapists I set an value to are the ones who employ methods used to rebuild speech in stroke patients and the like, those who concentrate on how sound is made, not quackery.