I can see your point. You don´t stutter while talking to yourself because there is no one there to judge you. You have permission to make mistakes. Instead of talking like a crazy person on the presence of other people maybe try to feel like you are alone in the presence of other´s. Act like you are alone even if there is someone there. You see is a very hard thing to do. At least for me. Even when I´m on the park and I close my eyes I feel like I have to open them sooner than later. I start to get anxious of what other people may think. Like everyone is looking me.