I don't have much to add, but I can 100% relate. I started stuttering in my late teens, even though I don't have a history of it occurring in my family (at least not that I know of). I believe it had to do with the constant high levels of anxiety that I was facing at the time. I have made progress, but I'm not 100% over it. I've been mostly working on the mental health side of things and it has helped, but I also believe that if you have a solid understanding of speech mechanics and accept stuttering, you can overcome it, because you develop the confidence that you're able work through any sort of block or repetition, which in turn also helps the anxiety around it.