I agree that slapping your father was not a very nice thing to do but we've all done things we regret in the heat of the moment (myself included). Just don't do it again obviously and if I were you I'd apologize to both your father and your mother and tell them why you did it. Maybe try to talk to one of your parents or both about why you're stressed and why you're acting the way you are. Maybe they might be able to help you relieve the pressure if you tell them exactly what a load you have on your back right now... because it is a lot and it's very understandable that you feel weighed down and confused.

I hope everything works out for you soon.