I guess my question is: Were you ever a theist? And if so what led you to doubt, question and ultimately give up that belief?
I know this is directed to the OP, but I feel like I can throw a thoughtful answer in as well. I believed in christianity until about two years ago.
The reasons that I began to doubt were numerous. First of all, the hypocrisy of religion in general, the idea that Earth is the only planet EVER with
life on it, with the only savior sent to Earth, and humans are made in god's image, which would mean that there are no other life forms in our
infinite and ever-expanding universe. I only truly began to question and give up my beliefs when I took a philosophy class last semester in college.
This is the one paragraph that truly changed my beliefs:
"Is god omnipresent, omnipotent, and totally good?"
"If so, then why is evil happening in the world?"
"If god is omnipotent, he has the power to stop all evil, and if he is totally good, he cannot be allowed to let evil occur, unless he is not totally
good."
"If god sees the evil, but cannot stop it, then he is not omnipotent."
Since evil still occurs, god either does not exist, or is not any of the things that humanity believes him to be.