When I was in my late teens, I began to doubt my christian upbringing. It started with me looking on a atheist website which was about the origins for belief in the human soul. I happened to look at this website out of sheer curiosity, but even then I resisted some of the things that was written on it.
It basically reduced the soul to a cognitive ghost, and it gave a more reasonable, scientific explaination for how the brain works. This lead me to question the very belief in the afterlife, because to me, if the soul does not exist, there is no place for an afterlife. Then God came next, this was a belief harder to shake off and I spent the next two to three months exploring other ideas like buddism and deism.
After much introspection and reflection I concluded to myself that the personal God I grew up to believe in probably does not exist and I fully embraced atheism. My mind was expanding so much at this time, I actually call this period of my life my "enlightenment" and grew to heavily appreciate science and free thought. One of the works that still inspires me to this day is Bertrand Russell's why I am not a christian, it was a perfect, logical manifesto of all my thoughts on God, atheism, theism, and agnosticism.
I began becoming outspoken in my atheism when I was in high school and this made me a target. I almost got jumped at lunchtime by a bunch of thugs at my school, they all gathered around me, questioning why I would even fathom an existence without God. I also had a biology teacher who openly promoted her creationist views on her students. She would ask each individual student whether they believed in evolution or the biblical account of creation. I thought to myself how onesided this was, trying to embarrass students in front of the class that didn't confrom to her(and the majority's) belief system.
But even through all this, I still speculate on the existence of God, ultimate reality or whatever. I try to be open-minded but still skeptical on the ultimate nature of the universe. I believe the big bang happened, but I don't pretend to have knowledge of the cause of the universe. I am ignorant and I accept that, as all of humanity is in a very small place in the cosmos. I now consider myself a agnostic atheist and even though
I don't believe in God, I still have child-like wonder for the vast, endless universe we live in. So I still have my doubts about everything, including atheism and science itself. It is important to have healthy skepticism and re-examine your own beliefs.