I've never known just what the "correct" expressions are. Either my face shows all too well what I really feel about something (which I don't always realise) or it's a perpetual gurn and grimace machine (or that's how I feel about it, anyway). I have a similar disconnect with my voice; I hate speaking loudly, and repeating what I say even more so. I have my animated/enthusiastic moments, and then feel as if I look like an idiot shortly afterwards. I've every sympathy.