I am confused. Is your question, does NOTHING exist, or is it does ANYTHING exist?
If it is the first, yes, I believe that nothing exists and is ever constant throughout the existent world. In between atoms and such.
If your question is does ANYTHING exist, that is something else entirely. We can be sure that something exists as of the present 100%, in fact it's pretty much the only thing we can be 100% sure of, simply because if something is doubted, there must be something to doubt. Further more, Descartes simply answers it with the term, "Cogito ergo sum." I think, therefor I am. By our own definitions of existence, the mere act of questioning your own existence shows that there is something to question in the first place.
Has it ever existed? That really depends on your definition of nothing. Some people say that the universe was created out of nothingness, whether through quantum physics. This seems to violate causality, which states that everything is caused by something else in turn. Causality would state that there has always been something that is existent. Also, basic principles of matter and energy state that there will, if proven correct, always be something existent, because we cannot create or destroy matter. It will simply change shape as affected by causality.