First of all, your "proof" is not really a proof.
Of course, god is infinite, in the sense that god has always existed and always will exist. You and I are also infinite in the same sense, as we existed as spirits before coming to Earth, and will once again exist as spirits after we leave it.
You can accept or reject that assertion, of course. If you reject it, and you are right, you will never know it. If, on the other hand, I'm right, then I'll be able to text you in the afterlife to say I told you so.
Secondly, if you think you can prove that god does not exist, then you are not an agnostic, but an atheist. An agnostic does not know whether or not god exists, but an atheist positively states that god does not exist.
Of course, neither a theist nor an atheist can prove their case, which is the natural argument for being an agnostic.
