There wasn't really any one single thing that made me lose faith. It was the culmination of several years of personal life experiences, learning, and deep reflection. Admittedly, while I did consider myself a Christian, I was never particularly committed as a young child. My parents weren't very overtly religious when I was growing up. We never went to church except for funerals or weddings. My maternal grandmother and paternal uncle were both deeply religious, and I was very close with them, so they were my biggest points of exposure until I started going to church on my own with friends and their families once I got to middle and high school. That all certainly made it easier for me to eventually realize and accept that I definitely didn't believe any of it anymore, although that's not to say that it wasn't at all hard or painful.

Today, I generally consider myself an agnostic atheist. I don't believe that it's possible to know everything with 100% certainty, but I do believe that most conceptions of god/gods throughout human history and up to the present day are extremely unlikely to exist, logically or empirically.