I suggest improving other parts of your life in order to improve self confidence. Exercise, healthy eating, learning, hobbies, whatever it may be. Concentrating and becoming very good at your interests/job will make it less about how you say something but more about what you say. Like /u/Mr_Quackums said. The problem a lot of people face when having a stutter is that they will 'let' the way they speak drag other aspects of their lives down that may not even involve speaking. If you're confident in your knowledge or your ability to do something, you then *know* that you are intelligent, regardless of your stutter.