Lack of Sex?

My boyfriend and I have been together for almost two years now, and have been having sex for about a year and a half. Lately we haven't been having sex as much as we used to, or we only do when we're drunk or something. He's leaving for college in a couple months so then we defiantly won't be having sex. Its not that sex is boring now, its just not as exciting as it used to be. Pretty much I'd like advice on what to do?