Oh relax. Understand this simple thing: You cannot prove that your god exists but worship him through faith. Faith which only you can see and understand. The rest is made up assumptions.
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Some numbers:
(1) Christianity: About 2.3 billion followers.
(2) Islam: About 1.5 billion followers.
(3) Judaism: About 14 million followers.
Looks like just shy of 4 billion people have this faith you speak of.
How do you know another's faith.... it's a personal thing. Faith is your own thoughts and beliefs.
Yes you can share a similar faith with others, which are shown by the numbers above, but your own faith is personal to you.
Hence my comments above....
It's easy to understand the basics of where your faith lies. If you had faith in God, you wouldn't be lying about the fact that you know He exists. Why not? Because then your faith would cause you to love Him, and you would be working on getting other people to be saved. As it is, you are only a liar.