Confidence is built upon past experiences—on what reality has consistently shown us. In simple terms , you feel confident if and only if your behavior is rewarded. One would be foolish to convince themselves otherwise, treating confidence as something they can willfully control. So, if your stutter truly stems from a lack of confidence rather than being a symptom of the stutter itself, then congratulations. Still, I ask that you leave room for my words, just in case my experience proves true in your case it may spare you unnecessary despair.