I think a lot of "scares" are paranoia. Like things are fine, but you have the niggling doubt in your head. For instance, never an obviously broken condom, but period's 5 days late!
I mean, I *know* I'm not pregnant. Or if I am, I'm very unlucky! Doesn't stop me worrying though!
Basically, me and this guy both ended up in bed not wearing much after a little too much alcohol had been consumed. I'm still a virgin because he didn't "enter" me, but got very close to it. I'm pretty sure he didn't even ejaculate, just pre-cum. And that was when he was further away from me.
Since then, I've had 2 periods 2 or 3 weeks apart. But neither have been "normal" for me. Sorry for the grossness, but it didn't contain enough lining for me! I've also felt bloated and had stomach aches and felt nausea for about a month!
There's explanations for it all. I've never been regular and I haven't been eating properly recently for example. And the paranoia has more than likely played a part too! Mainly with the nausea I think! Still hasn't stopped me worrying.
I dread to think what I'll be like when I actually have sex! But it won't be any time soon.... I know that for sure!
HOWEVER, I highly doubt you have anything to worry about! Taking the MAP within 2 hours of it happening very greatly reduces the chance of pregnancy. If your girlfriend still hasn't has a period this time next month, then start worrying!