This is what always happens! Friends With Benefits situations, like the one you're in now, are always temporary. They either turn into relationships or turn into two people that hate each other.
Sex is a powerful thing. It can turn to love, or a reasonable facsimile of love, very easily. When that happens, people need to make some very quick decisions. For you, and folks in your position, here are the questions that you need to answer:
-Would he be a good boyfriend?
-Would you be a good girlfriend?
-Do you two have anything else in common besides good sex?
-Do you both have time for an actual relationship?
-Do you think he likes you?
You're going to need more Yes answers than No answers for this to become a relationship. So figure those things out before you decide to just cut him off completely. Because if you like him, he likes you, and you both want to give this a real shot, you owe it to yourself to try.