Hmm, I think I have this problem too. I talk fine when I'm not thinking about my lips moving, but as soon as I start thinking about it, I start going into an unconfident mumble.
Also I have a fear of people smelling my breath, and when I think about that too much, I worry about moving my lips too much in case they might smell it - although I know I'm not the type of person to have a strong breath (my mum would tell me if she smelt it because she's the sort to tell anyone because she gets easily sensitive to smells like that, well she wouldn't tell friends but she would tell close relatives). Plus I don't smoke, I clean my teeth regularly, and I have generally healthy teeth. But knowing all that still doesn't make me feel any less afraid of the possibility of someone smelling my breath.
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Female