Have you ever asked him this question? I don’t know what his answer would be, of course, but if he doesn’t want anything to do with God now, I doubt if getting married will change him.
But God can change him—and that’s why you should be praying for him. Logic alone won’t make someone into a believer, and neither will any other argument or appeal (although God can use them). Only God can convict a person of their sin and their need for His forgiveness, and only God can convince them of the truth of the Gospel and its promise of new life. Jesus said, “No one can come to me unless the Father has enabled them” (John 6:65).
I suggest you also seek to discover why your boyfriend doesn’t want anything to do with God. Often, I’ve found, it’s simply because a person wants to run his or her own life, and doesn’t want God to interfere with whatever they want to do. But a self-centered, stubborn attitude never provides the foundation for a strong marriage, and leads to numerous practical issues (such as how you’ll raise your children).
Make sure of your own commitment to Jesus Christ, then prayerfully seek His will for your future. He loves you knows what’s best for you. Don’t be tempted to go down a wrong road, but trust Him to lead you to the husband of His choice—someone who loves Christ, and will love you, as well.