During these moments you have to ask why are you feeling inferior, losing confidence, etc. "Is it fear? Are you catastrophizing?" And so on... You may benefit from traditional therapy. Also, try to see if there are any stuttering support groups in your area. You can learn so much from others who have been in your shoes. For me, I gained confidence as soon as I accepted my stutter. That may seem backward at first. But you need to love yourself, "flaws" included, in order to feel good about yourself and be confident.