When my wife and I first met, we weren’t really religious at all. We were both good people and all, but after we got married, I started to really examine life and the meaning of life and how it could have all started.
I studied everything from science theories, the Bible, other religious views and more. After thinking and studying everything, I concluded the Bible was the word of God, and Jesus was the messiah and God’s son.
After that, I started to share my beliefs with my wife. Like I said, it sounds kind of like your situation. She wasn’t really religious, but a good person and didn’t care or think about religious topics much.
But I slowly started sharing my beliefs, and I backed it up with how I came to my conclusions. I didn’t “FORCE” her to believe it, and I didn’t annoy her or bug her or anything. I would just try to bring it up. For example: I would say things like, how did we all get here? What is your opinion on it? Then I would listen to her, and then share mine as well. Don’t argue, just hold to your beliefs.
We would just sometimes openly talk about it. Try to find ways to bring up how life started. Try to show evidence for why God is real (there is plenty online if you need help). Again, be careful because people don’t like to be told what to believe.
Hopefully, you can find ways to openly discuss things about how life began, why you believe in God, and more positive things about it. God makes the most sense of why and how we are here, and hopefully you and your boyfriend can begin growing in faith and becoming more interested in it together (especially him).
By the way, now my wife and I believe basically the same thing about life/God, we have really developed a deep faith in God, and we read the Bible to each other, pray together, and more. So keep hope and faith that he will open up more. Sometimes it takes time.