Grammatically Incorrect(?)

Using big words(ones that are bigger than you) doesn't make you any superior. Is my grammar correct? Lol. 'Using big words' is a singular verb right so "doesn't" is applicable?

Oh my. Did I just type that? Gah. I always tend to question myself especially when it comes to my grammar, spelling and vocabulary. Must be the effect of the upcoming entrance tests or am I really just losing it?