I think the difference is that only a relatively small number of people have true 'faith' in atheism. Many people, yourself and myself included, are agnostics who's general guess at what's true is no gods, but who accept that there might well be more in heaven and earth that is dreamt of in their philosophy, Horatio.

I tend to mentally divide it into atheists and Atheists ('god(s) don't/probably don't exist', and 'it is impossible that god(s) exist' respectively), and agnostics and Agnostics ('I don't know if god(s) exist' and 'It is impossible for anyone to know if gods exist')

Under that description, you're probably a little 'a' version of atheist.