Took Plan B... got "period"..??

So I took Plan B (I know it's really bad for you, but better safe than sorry) and about a week later I bled for about a day and a half and I thought it was my period coming early, but it wasn't. Well, anyways, today I'm due to have my regular period and I'm scared I won't get it because the condom broke two days ago and I didn't want to take Plan B again. Was the bleeding just a side effect of the pill? Help!!