Hi!
Anything is possible when it comes to pregnancy. It is unlikely to be guy #2, but you might want to cancel this cycle and take the morning after pill just to be sure. It can be used for up to 5 days after the "event". It might of course also prevent a pregnancy between you and guy #1, but unless you are ready to settle down a bit, that might not be such a bad thing! Think twice before you "try" because once you are pregnant, your partying days are at an end!
Good luck!
Dr B
it's highly unlikely that the other guy is the father as long as the condom didn't split or break!