I would worry if you did stutter when you are alone. I discovered after 20 years of researching on how the brain learns that stuttering is a brain anomaly. I found that my brain is wired differently than that of a fluent speaker. I decided to rewire my brain to match the brain of a fluent speaker. When I was able to accomplish this I too became fluent. I base my success of becoming stutter free on the Valsalva principle.