[Nova]

Even though ovulation times aren't an exact science since every woman's menstrual cycle is different, it's nearly impossible for you to be pregnant if you had sex yesterday and then got your period tomorrow. Typically you ovulate two weeks before you get your period. Meaning, two weeks before menstruation, an egg is released for fertilization. Sperm can live (but majority don't) in your body for a few days, that's why you have a fertile period before ovulation. The egg can really only be fertilized in about a 12-24 hour window before it dies.

ANNNND, if you think about it: there are millions of sperm in an ejaculation. Many are weak and won't survive, and your cervical mucus can be acidic and kill some at certain stages of your cycle. Then of the hundreds (think of that, MILLIONS to HUNDREDS) that may be capable of making their way to your fallopian tubes, must be strong enough still to break through your egg's membrane.

So take a deep breath. Although it only takes ONE sperm to make a baby, think of all the other factors that are on your side.