I've been working at my confidence because I'm very introverted and shy, however I've noticed if I'm somewhere like Subway that requires me to have a smile and sound all happy, I naturally respond with these main lines: "Hey, yep, yep, no, no, thanks" and I do this while maintaining eye contact, it's weird and I feel robotic, I feel extremely tense.

It's worse when the girl will say "sorry, what was that? would you like a bag?" and I'll give a awkward "yep". I don't know whats wrong with me but I feel like I give a pissed off vibe to girls and I leave them with a bad taste, where as other guys leave them with a smile.