pls help!!

last week on friday my bf and i had unprotected sex, on saturday (a week before my period) i took a plan b and normally i get bleeding after and i didn't..i started birth control on monday and on Thursday/halloween i drank a lot. friday i was hungover and today (saturday) my boobs are sore, my back hurts, i'm unbelievably bloated..should i be worried about pregnancy or is it just because of my hangover?? someone pls help and if you need more details pls ask!!