How awkward do you feel when a guy you're not attracted to is into you?

This happens to me often. I would be really nice to a guy, and he takes it the wrong way and then tries to go out with me or tries to flirt with me. Is it abnormal for me to feel totally weird and awkward in these situations? And I would never ever have the guts to say I'm not interested, because maybe I'M the one getting the wrong idea. Haha. Ahh awkward awkward awkward! Anyone in the same boat?