Have you ever asked yourself what's missing from your present relationship? You might answer this in various ways, but the most important thing that's missing in this relationship can be summarized in one word: commitment.
That's why marriage is so important, because it includes the one thing you'll never be able to have in your present arrangement -- namely, commitment. When a man and a woman get married, they make a solemn vow to be committed exclusively to each other as long as they both are alive. Not only do they make this vow to each other but they also make it before others -- and most of all, before God. Jesus said, "Therefore what God has joined together, let man not separate" (Mark 10:9).
Why won't your boyfriend talk about marriage? The reason is obvious: He doesn't want to enter into a committed relationship. Right now, he has everything he wants -- and frankly, if he gets tired of it (or of you), all he has to do is walk away. And I suspect that's exactly what he'll do, sooner or later.
The most important advice I can give you is to urge you to stop leaving God out of your life. God loves you, and the most important thing you can do is repent of your sins and give your life to Jesus Christ. Then leave your old way of living behind, and put your life -- and your future -- into God's hands. His way is always best.