How do I bring this up without sounding like I am paranoid about him dating other people?

If he isn't exclusive already, guess what, he never will be - he'll only say he is, or just dump you.

I think you've waited too long to bring this up - if you do now, it will just sounds like your a control freak - instead, try talking to him about what he sees happening in his life down the road

Transition your idea of an exclusive talk to a future talk.

Cheers

If he truly likes you he won't be stupid enough to make you want to "pull out. " Some guys are commitment-phobic so while he's still seeing you a couple of times a week (that's a good sign that he is still into you) he might not want to want to be "exclusive" yet due to fears of commitment.
With guys like these, it's really a matter of a time when he's really into you and have decided to commit to you. You'll have to make him super like you in one way or another. Or if you're already doing your best to show that you love him (don't tell him, just show! ) give a time frame to sort things out, for example, by the end of the month. If by end of month he's still the same kind of diluted reaction, then decide that he is just Not That into you. Tell him about two weeks before that you feel like you want to break up (or just the words "opt out") and it will certainly alert him. Then watch his reaction, and you'll get your answer that way.

Hope this helps.