I guess my situation is quite similar. In general I'm stuttering in two cases: immediate stress (everything was fine and now I have to deliver a public speech so I'm stuttering) or long-term stress (I had a terrible week and now I'm telling story to my friends, situation is fine, but I'm wore out so I'm stuttering). I started working with therapist few months ago and she said I might have anxiety. I'm not sure what is the correct diagnostic process, but I can tell that having clear mind helps me a lot more than exercise and speech therapy I tried to have at school.