Fifteen is a very young age to have a baby. Not only does it cost a fortune to raise a child well, it takes a lot out of a grown woman....it is physically exhausting and emotionally draining, even for healthy women. You are still in your teens and have not stopped growing mentally or physically yourself, so if you are considering pregnancy or if you are pregnant, you should really invest in the help of a nutritionalist right away.
It is very possible and almost likely that you will get pregnant 2 to 3 days before you ovulate, granted that you did release an egg at the time. Although the day of ovulation only lasts 24 hours, sperm which has been introduced earlier can last as long as three days prior and can fertilize the egg at ovulation.