You can ovulate at any time during the month. When you ovulate is when you can get pregnant.
Unless you are charting, and temping, there is no real way to know exactly when you would be ovulating. It is not a reliable birth control option if you are trying not to have children. Go to planned parenthood where you can get free or low cost birth control. They can educate you on what would be best for you to take/use.
Good luck!