The voice in your head is the voice of ignorance and the voice of Shaitan.
How can it be possible that God doesn’t exist when even those that deny his existence.
1. Can’t prove that he doesn’t exist
2. Hate him intensely even though they believe that he doesn’t exist. Like hating the bogey man.
3. Give you ludicrous ideas about the existence of life.
It doesn’t matter if you are born into the right religion or not. What matters is when the truth is presented to you, that you don’t conceal it.
People that refuse to acknowledge God, do so to either avoid any obligation or so that they don’t credit the abilities they have to being a gift from God.
So does God exist?
According philosophical argument and logical deduction the only truth lies in their being a supreme force that caused all that exists. And this force according Biblical and Islamic texts is God.
You need to start researching more on this subject, begin here: