Am I acting desperate/slutty?

With him being a cop and in college, he probably isn't worried now about going to another level and doesn't want to complicate things for awhile. So I'd be content for now with what you have. You're not being slutty, since you're not sleeping around for just any guy to have casual sex with. But since you've already had sex with this guy, I wouldn't just shut it off completely, unless he gives you a reason to.