I thought of suggesting that, but if the OP does happen to ovulate on the day of the condom ack (which she said was likely), Plan B wouldn't do a whole lot of good -- there was a recent post about this, in which I learned that Plan B has been shown not to have any implantation-interrupting effects.

It is, though, a generally good thing to have around if one is using condoms alone! And it'd probably be worth taking anyway, just in case ovulation hadn't happened yet, to try and block it.