could i be pregnant? please help!!

me and my bf had sex four days ago, we used a condom but it broke and he finished inside. this is my first month on birth control and i was on the last pill of the 3rd week. i took a plan b (take action) just to be safe. i am now on my 4th sugar pill but i still haven't started my period. i was having bad cramps and bloating but it has stopped significantly. should i be worried? can plan b make you skip a month?