Hi there!! I hate to tell you this, but your case is not unique. A large majority of people who stutter do NOT stutter when they are alone. In addition people who stutter may not stutter when talking to robots, pets, babies and/or small children. You can hack your brain by going to go see a speech therapist trained in avoidance reduction therapy and acceptance and commitment therapy (ACT). In addition you may learn some techniques to make the stuttering moments easier. Good luck!