You could always do what my husband did. When he was married to his first wife, she became a devout Christian. He followed along to church every week, volunteered to do church stuff, and even led worship services in his home for a few other families when they lived overseas with no readily available churches. He bent himself over backwards to try to fit in the mold that she wanted him to fit in, trying to believe, pretending to believe, forcing himself to believe. But he didn’t believe. And after bending so far, it caused him (with some other major issues) to break. They got divorced.
And that is why he is now my husband. (I met him several years after the divorce, and had no part in his marriage’s undoing.)
If you do not believe, it may be that you can pretend for a while in order to get married to the girl you love. You may even believe, in time. But if you do not believe, really do not, it might be a lesson in futility. And there might be someone else down the line, who you don’t know yet, that is more in line with what you really believe.
My guy was married for the first time at age 19. He was a dude too young to get married, just like you might be. It took him almost 20 years of pretending before he finally got out. I hope that if you discover that you aren’t a good fit to be married to a church lady, you can do something sooner. And if it does work out, I wish you much happiness. :)