I made the same mistake with one of my exes. You cannot push or force someone to love you. If someone cares about you, then you should be together. There is no grey area. Secondly, you're probably scaring her. Once you get to that point, game is completely over. Never ever do that.
So here's what I say. A relationship is like rugby. It's fun to be in there and to have fun. But you also know that you can get hurt playing this game. Now if you get hurt, you have two options. You can stay on the ground weeping or you can get up, catch your breath and move on. I know it hurts, we've all been there. Learn from your mistakes. Don't give her the satisfaction of seeing you in misery.