This might not be a stuttering thing, and I don't quite feel comfortable saying anything concrete about it, because I'm no expert. Could we be dealing with a behavioral maladaptation or something? I mean, it's likely that a person who stutters is less familiar with social interactions in their developing years than the average, simply due to shying away from occasions for communication, but whether that's what you're experiencing, I can't say. If you're curious, there are various tests that can be performed, as part of a potentially diagnostical route. But it might just be that a setting with speech is hard for you, and hence you don't have as much surplus to act with.