The way you worded your post (and tell me if I'm wrong!) made me think it sounds like you maybe don't quite know him well enough to trust him with a disclosure or even having sex. If so, respect your gut and slow down the physical stuff. If I'm way off base, you can tell me to shove it. ;-)
I'd never tell you to shove it! :) You're right. Technically we haven't known each other for more than 2 weeks, but we hung out all day every day for 5 days straight. So, to me it's like we took at least 4 weeks of dating and condensed them down to one long holiday weekend. That's why I want to tell him because I'd like nothing more than to be physical, but I'm so scared to disclose.