During your window of ovulation, your most fertile time is considered to be about 5-7 days long. An egg is only available to be fertilized for about 12 – 24 hours. Since sperm can live in the body for 3 – 5 days after sex, and the egg is available for one day, you must identify those 5 to 7 days and have sex just before, during and even a few days after these days if you want to get pregnant.