So women can only get pregnant when there ovulating?

Yes and no: Conception can only occur if the women ovulates and is more likely to occur if intercourse occurs closer to the time of ovulation. However, a women that has sex one time six days before ovulation has about a 3 out of 1000 chance of conceiving. Her chances are about 1 out of 10 if she has sex near the time she ovulates. By about 24 hours after ovulation it is too late to have sex and conceive.