Aimee,
You mentioned you had already had sex with this guy before. Was he not angry about you not disclosing earlier?
I only ask because I'm in the exact same situation right now: we've been on a few dates and had sex one night after some drinks (with protection of course). He is coming over for dinner this weekend, and I want to disclose to him so our relationship can continue to grow without lies and omissions. I feel very guilty about not telling him a few months ago when we first had sex, and now I feel as though he will be angry at me for not disclosing right away.
Any advice would be wonderful!