stop being ashamed of my sexuality; by that I mean stop being afraid of being a sexual being

For some reason I get so nervous at the idea of introducing a guy I’m seeing to my parents, especially if he isn’t that conventionally good looking. It sounds horrible, and its a habit I really want to kick. My parents know I’m sexually active, and by most people’s standards this is normal, after all I am 23.
But I keep feeling embarrassed if the guy isn’t that good looking by other people’s (esp. my parents’) standards. I imagine that everyone will imagine me having sex with the guy and unless he’s a total hottie, this embarrasses me deeply. I guess I have some issues with expressing my sexuality (albeit heterosexual).Can anyone offer any advice?