If you turned him down I'm wondering if you're serious. If you actually want to date him, then show that you're interested. If you go back and forth he'll probably be skeptical about dating you (since you seem so on the fence about it)...even if he is still interested. Also, make sure that you're not misreading him. It's hard to tell if someone is fake-not-liking you, so try to confirm that he still actually likes you.