Had the same issue as a kid. Being in speech therapy was kind of depressing in my eyes then. And whenever i was in a depressive state I wouldn't stutter. But the minute i left the office i would always go back to stuttering 10 fold. For me stuttering seems to be linked to subconscious anxiety that i cannot pinpoint. Have no idea what causes it. Or how to fix it. But i can physically feel the anxiety in my body when i do stutter. Tight back, neck, and jaw. Short of breath and upper chest pressure. Not caring about the situation im in is all that has proven to help in my experience