I have found for myself that I'm actually more fluent in stressful situation. I know it sounds strange and kind of contrary to popular belief. It's like your brain kicks to another gear and tells you "ok, that's serious, there's no room for stuttering here". This doesn't mean my stutter disappears in these kind if situations, but I find myself delivering my message faster and more understandable than other time. Maybe the brain releases some chemical that boosts you nervous system thus reducing stuttering idk..