1. “Echar un polvo” instead of “estar hecho polvo”
You’re exhausted, which is what you wanted to say, but that’s the reason your brain has just failed to accurately remember the idiom you were trying to use. Why is everyone looking at you like that? Because instead of saying “estoy hecho polvo” (“I’m really tired”), you’ve just said “echo un polvo” (a colloquial way of saying you have sex). Idioms are tricky!