hey. I'm 20 and developed a stutter when I was 12. It happened because of a belief I held (still hold) that anything I have can be lost, even my ability to speak, and after some people told me that making fun of my friends stutter would give me one-it got worse. the more aware of it I became the more resistance i felt. Look up the Monster Experiment. Just by thinking about their voice too much, the researchers taught the kids to stutter. I've improved it a whole lot since but it still is here on and off.