The research done on stuttering indicates that people who stutter have the same range of psychological traits as the rest of the population. It’s very unlikely that stuttering has a psychological cause and it seems increasingly clear it has a neurological cause (based on current research). There was an interesting study recently linking stuttering to a malfunction in the part of the brain that initiates speech. https://www.eurekalert.org/news-releases/935331 It may be helpful to address things like an inferiority complex that exacerbate the problem, but most likely your thoughts and feelings didn’t cause your stutter. It was outside of your control.