Your chances of being pregnant under these circumstances are almost nil, provided that you used the condom all the way through and had no contact between his and your genitals after you were done and he removed the condom. A far more likely explanation would be that since you were a virgin when you started this, you're likely pretty small inside. If he was of average size or larger, think of it like your uterus got mugged. With any substantial amount of pounding on the cervix, your uterus sheds a little bit of it's lining and causes the spotting. Your body becomes confused and you may not have your period on time. I ask questions myself about "iffy" methods of contraceptions because I don't know all there is to know about this, but I do know for a fact that if a condom is used properly and it doesn't break or leak, then there's really no way for the sperm to find it's way inside you. If there's no way that the sperm got inside you, then you are not pregnant. If you didn't use the condom properly, it's still most probable that you aren't pregnant as long as he didn't come inside you without the condom, but now there's a chance, albeit a small one. I would suggest that you go get a good home pregnancy test and read the directions carefully. We could speculate a lot on this and explore a lot of possible scenarios, but unless you do a test, you still won't be 100% sure.