Your body would not even know if you was pregnant. It takes 5-7 day for the sperm to make it to the egg. But get the morning after pill. Also as a female you need to protected yourself from getting pregnant if that is not what you want. If you are under 18 go to your mother or you can also talk to you consoler at school and they can help you tell your parents and help you get the things you will need.
Go get the morning after pill asap!! Don't chance it!!
if you're not trying to be pregnant at the moment its best if you do take the day after pill but if you want to be pregnant then you don't need to take its your decision doesn't hurt to take a pill or not it's just maybe it'll make you feel better just in case