He's talking about how he doesn't want to fall in love, and wants his lover to just be playing him as well. But she starts to fall in love with him, and he starts to too but is too afraid of what will happen and tries to stop their romance. Thus leading to hurting her, and almost deepening his feelings for her along the way. And he wonders how long he will continue to love her, or how long he will stay because he is too afraid to truly show his love.