Hello i have a very big problem please help...

im 15 ok my girlfriend came over today and she started to toss me off. we always do this so its nothing out of the ordinary. and she wasnt doing it quite rite and was hurting but i didnt say because i didnt want to offend her. well then we started to have sex for the second time (the first didnt have any problems) and i had a bit of trouble getting it in and didnt know why... but eventualy it was in, afterwards it was reallly starting to hurt now and i couldnt walk and if i did i was limping very bad (which was kinda amusing for her) after she left i went back up to my room to see wot all the fuss was abotu down there and it turned out that my penis had swollen up an extreme ammount ont he bottom of my penis and a little bit on the top. the promblem im having is i cant tell my dad just incase he was angry that i was having sex and the second problem is that i have school tomorow and im nto sure im up to it. how long will it take for the swelling to go down?? also we wasnt using a condom if that helps??