You could be firing blanks that will give you less sleepless nights

If you don't know enough about getting a woman pregnant, then, you shouldn't be having unprotected sex-with anyone. Why sire unwanted ****-the world has enough of them already. And you are 21?????

In general there is 3 or 4 days between ovulation when the certainty of conception is at its highest, there is no precise formula. the risk of pregnancy in your case is low but not impossible. Its a huge and complex subject where you may find thousands of articles on the internet or directly face to face with a doctor. Since the deed has been done there is only time that can give you the definitive answer

She sure can, more like taking a risk than a memory lapse