I don't really have any specific recommendations. I have a feeling that tackling the issue of confidence is individual for each person. What helped me was doing gut healing via diet, a lot of juicing, therapy/emotional work. I've figured out that my gut health is directly related to confidence and fluency levels. Within the course of 24 hours I can go from major blocking to complete fluency (like a normal person who has no stutter) depending on how my gut health shifts. There's no literature on gut health and stuttering so I don't know how applicable my situation is to you. Perseverance and willingness to think outside the box have helped me out a bunch,