Seems like people on here move pretty fast! OP if you're a virgin and you want your first time to be 'special' and all of that, I can see wh you want to 'secure' things. But you should know that a lot of guys are not exactly keen on exchanging commitment for sex before they even know if you're sexually compatible.
Personally, I have to really like a guy and know that he likes me before we go to bed together. But after that, it's just about waiting and see how intimate you get. I don't date usually date multiple people at the time. I can go on a date with a guy while I'm seeing someone else, but I don't sleep with multiple people at a time. You need to take this a bit by feeling and cannot always play by 'rules'. There are other things which are far more important than how many dates - such as how intimate and close are you, are you compatible both personally and sexually, do you open up to him and does he know the real you. By that I mean, if you were to discuss exclusivity, does he know what he's getting into and what kind of girlfriend he can expect you to be?
Also make sure that if you have had minor arguments or disputes, that you let a couple of weeks pass before you can expect him to bring it up. Things have to be smooth-sailing for some time before you can consider being a couple. Don't expect to make up after an argument and discuss commitment the next day.
I'm in this sort of situation myself with a guy. But for me it depends a bit whether he'll find a job in town or not. The practical things are just as important (if you, like me, are not interested in long distance).