We all have. Bullying is not limited to people who stutter. People who are too tall, short, fat, thin, smart, dumb etc all will have suffered from some bullying at some point. I have received a few comments from adults and honestly they have just been human trash. Mean for the sake of it. I am sure they give the same shit to people who don't stutter. For several years after school I struggled in personal relationships because I thought people were secretly talking behind me back or thought less of me. Letting that shit go was liberating. I have positive experiences with most people I interact with and I focus on these experiences. If I fail at talking I sometimes beat myself up and I am working hard on controlling that. For me at least, I find my confidence and fluency depends on my general outlook and I work hard on staying upbeat.