Birth Control Help

Hey ladies so I'm on birth control and I started my cycle this week Tuesday evenings it is now Friday and my cycle seemed to have stopped. Usually it stops on Sunday or on Saturday evenings. Should I be worried? 
Btw last month I took plan b after my BF told me our condom broke. Do you think that has anything to do with this short period? 
Everything look normal like anyone of my other cycles yet this one just seemed quite short. 
Thank you for the help!!