Why is it that the person you want, seems to never want you back?

Right now it seems as if the person I want, doesn't want me back.  Why is that always the case?   When I first started dating him, he was the one chasing me, and I wold look at the phone when I saw it was him calling and think "again"?  now things seem to have switched......and I feel a bit like I'm chasing him.  I think it's time to disappear from his life for thirty days to see what happens.....I'm just not a natural at playing hard to get.  Why can't I act like I don't care when I do?  Ugggggh, I need some practice at concealing what's in my heart.........