It is extremely unlikely that you will become pregnant right before your period. It is fairly safe to assume your ovulation occurred between days 11 and 21 if you're a woman who typically has a 28- to 30-day cycle. Fertilization of the egg ejected by the ovary can only take place between 12 and 24 hours after ejection. Thus, the days right before your period are the best to engage in sexual activity without worrying about getting pregnant. Longer cycles are associated with more "safe days" and shorter cycles with fewer days before your period. Right after your period, you can get pregnant since you're moving into your fertile window. When you stop bleeding on Day 6, have sex on Day 7, and ovulate on Day 11, there is a chance that you will still have sperm from Day 6 in your fallopian tubes that can potentially fertilize the egg. The chances of becoming pregnant are higher after a period rather than before one.