CBT has been proven to significantly decrease anxiety. This program is specifically geared towards adults who stutter. In CBT, you identify unhelpful thoughts that keep you stuck and learn to change these to become more confident and less anxious. By changing your thoughts, you change your behaviour and your emotions. The key thing in this CBT program are social experiments. You identify situations that you usually avoid and learn to not see them as a threat anymore. I would highly recommend giving this a try. It was developed by one of the world's leading experts in social anxiety in people who stutter. He leads you through the program.