If you are ovulating at the time of intercourse, the sperm and egg will unite on the day of intercourse to form a fertilized egg, which will then enter the uterine cavity in about half a month, and a blood test for HCG will tell you if you are pregnant. If ovulation has not occurred at the time of intercourse, the sperm will wait for the egg in the fallopian tube, usually for two days, at most three days, after ovulation, the sperm and egg will unite to form a fertilized egg, which will then enter the uterine cavity.