I think it's just the fear and anxiety. Sometimes I don't really think about my stutter and just accept that I'm like that. Try to not worry about it or at least to not think about it. I know that it's impossible not to think about something but it works for me. Not thinking about the whole stutter thing but getting a whole new mindset. Also, try to not think about the speaking beforehand. I speak better when I have to quickly react to something. Anyway, hope you will do better :3