I strongly urge you not to do this, but to accept the fact that your relationship with her is over. If it is God's will for you to marry someday, then you can be confident that He has someone else already chosen for you. But don't try to restart this relationship.
Why am I so emphatic about this? The reason, frankly, is because I suspect that lurking inside of you is a secret hope the hope that this relationship can begin again. And when it does (you hope), your former girlfriend will realize that she's made a mistake, leave her husband and marry you.
But listen: Don't be guilty of breaking up her marriage or even trying to break it up. If you did, you would be guilty of a very serious sin in God's eyes. Not only that, God would not honor your marriage. Jesus' words concerning marriage could not be clearer: "Therefore what God has joined together, let man not separate" (Matthew 19:6).
Instead, I urge you to discover a different relationship a relationship with God. God knows all about you, and He loves you and wants what is best for you. He loves you so much that He sent His only Son into the world to die on the cross for your sins. By a simple prayer of faith you can invite Him into your heart today and if you do, your life will never be the same.