Like Aletheia said, when having sex there is always a risk of pregnancy unless the woman or man are "fixed" (or for some reason unable to conceive that's NOT by choice) OR the girl is already pregnant.
That being said, the spotting and sickness might not have been a big deal. She could just be generally sick. HOWEVER, if you guys had sex, say, a month ago too, I'd suggest having a pregnancy test to be sure. If you both feel like there is legit reason to worry AND SHE PROCEEDS TO MISS A PERIOD, I would go get a pregnancy test (times 3) BUT if she doesn't miss her period I see no cause for concern for the time being. Hope that helps
