Don't text, email, or call him back right away. There is this book by Sherry Argov that's very insightful and funny. It's called Why Men Love *****es, and another one is called Why Men Marry *****es, lol.

You should never respond to every text or call right away since that will let him know that you are desperate (in his eyes), needy (again, in his eyes probably), and that you have nothing else going on with your life. Also, men love the thrill of the chase. If you don't make him chase you, he'll loose interest quickly.

Also, maybe he's not into you, a player, married, has a g.f, or is just looking for sex. Forget about him and move on with your life.