I’ve cured my stuttering almost completely using this technique. The King’s Speech (book) is a great piece of evidence. The other part lies in your beliefs - if you believe it isn’t accurate, you won’t cure your stuttering. But if you believe it works and it’s accurate, and continue to push yourself to get better, you will eventually cure it. It’s simple, but not easy. Like all habits, it takes time. Lots of time, but it’s not impossible. The more difficult part is convincing yourself of the hard truth. I’ve helped three others with this technique, big improvements in about a month. After that it’s just the sticking points which need to be dealt with. However not all stuttering is caused by a breathing problem; but OP’s one, where he stutters when alone, is a definite sign of a breathing problem, since there are no other factors, like anxiety, involved.