That makes you a Skeptic, not an Atheist. A Skeptic is nearly sure there is no god, in other words a Atheist who doesn't have Unqestioning Confidence.
Duck 1: An atheist is simply someone who lacks a belief in God. Skepticism is a questioning mentality.

Actually the definition for Atheist is "One who disbelieves or denies the existence of God or gods." so you are both kind of right on that one. If someone denies the existance of God, they believe there is no God.
Duck 2: Replace God with Santa Claus. I don't believe in God any more than you believe in Santa Claus. I'm an atheist, and if the majority of people believed in Santa, you'd be an 'asantaist' or something. This has nothing to do with how sure we are, as few people would not admit they're wrong if something proved to them, by their standards, that they were. You suggest that to be an atheist, you'd have to deny that God exists even if he proved he does, which demeans atheism and is just plain wrong.
All atheism means is that you do not believe that a god or gods exist.



Yet each man kills the thing he loves--
By each let this be heard...
The coward does it with a kiss,
The brave man with a sword!