The only way to conquer social anxiety is to slowly put yourself into situations where you’re socialising, however for a stutterer this can be different. How are you at ordering food? If you believe you are not great at that, start there. Anxiety can exacerbate stuttering but it’s not the cause of it. Try reading, out loud, to yourself. See how you go with that. Build confidence, slowly. Last thing I’d like to add is that you want to think of any sort of anxiety(fear) you have as an inner beast and you constantly need to reassure that inner beast that it’s not in control and you do so by engaging in actions that build you up and don’t build up the inner beast. For example, when you want to speak to somebody but you’re afraid that you’re going to stutter, you disengaging from that opportunity to talk to someone is feeding that inner beast. These “inner beasts” can be anything, such as a fear of a spider or fear of heights. Of course it’s subjective to the individual but the mechanism is the same for majority of fears that attempt to plague us.