HELP!!! Do I say something to him?

I've met a great guy and we've been out a few times (been seeing him since December). Our schedules are opposite of each other so we don't get to spend a whole lot of time together maybe once a month. We communicate through email and by phone. My question is is that it is casual now (we have slept together) and I would like to make it official. Am I out of line to say somethng. Tell him that I would like something more with him and if he doesn't than I can just walk away and find something else to spend my time on. I really like this guy alot. Do I take a chance and say something or hold back and wait. He's the shy type and real homebody and an only child and I don't know if that adds credit the the situation or not. I know he's not out sleeping around. What do I do? What do I say to him?