Ovulation happens usually 2 weeks after the start of
your last period, and that can sometimes cause your breasts to be sore
. Only after ovulation, which is when your body releases an egg, could you get pregnant. If you have sex around ovulation and your egg gets fertilized, it takes at least 5-7 days to implant in your uterus. THEN, your HCG levels in your body go up and tell your body you are pregnant. Which is why you have to wait almost to your next period to take a pg test.