Mortified! We've only got 2 and there is no way I want another one! That being said, if it did happen we'd just get on with it.
I did have a scare recently when my period was a week late, I was fairly certain I wasn't but it was very worrying all the same and me and dh did have that conversation about what if.... he said he'd support me no matter what I decided, to which I replied that there was no decision for me, I'd just have to deal with it, and he said he was relieved because he would have said the same.
So at least we know where we stand! But yes, I would be mortified and unhappy.