This patient support community is for discussions relating to relationships, abstinence, arousal problems, birth control, cohabitation, commitment, communication, couples counseling, desire, sexual technique, and sexually transmitted diseases (STDs).
This is a matter of integrity to me. I'm wondering...if you have a fight this weekend and storm off, would that mean that you can go out and have sex with someone else by telling yourself that you thought you were broken up with your girlfriend? I've heard of people doing this--I actually worked with a guy who would have a fight with his girlfriend and break up when he wanted to go out with someone else.
There's no "technicality" involved here, imo. I'm wondering why you don't tell her. If you weren't yet together, there shouldn't be a problem. If you weren't going out with your girlfriend at the time, why do you feel guilty?
I think guilt is pretty telling...it's a moral compass for me--if I feel guilty about something, it's usually because I SHOULD.
If you were to tell your girlfriend tonight, how do you think she'd react? Was the other girl you had sex with someone you see on a regular basis? Is she someone who hangs out in your circle? Or was it a stranger or someone else you will likely never see again? Also, how did this other girl view your sexual encounter? Did she know you for a while and was she under the impression that you liked her and that she would likely see you again? Or was she just having sex with you with no intentions of seeing you again?
The fact that you are feeling so guilty and awful about it is a good thing. Are you certain you are clean? Don't you have to wait 3 months or something (maybe longer?) to be certain about HIV?
What this comes down to is this: if you love her or care at all about her, you'll tell her and let her make a decision about it on her own--if you don't truly love her and it's all about you and getting what you want, you won't tell her. You have a chance to do the right thing after doing some really wrong things.