I understand even I get super anxious and depressed too. Maybe that's the reason. I have always been a sensitive person. I almost feel like my breathing is irregular and these double breathes are frequent. Though there are episodes where I am fluent and realised I am not anxious during these periods. Also, I have noticed that masturbation does increase my stuttering. Yeara ago I read on nofap sub there is some correlation between stuttering and masturbation. I don't know if it's really a cause though.