My girlfriend's period started last Feb. 14-16 and ended at Feb.19-21 . We had contact last Mar. 16 with and without condom. This Mar. 21 we had another contact but the condom broke and an "accident" occurred. She already took her first dose (4 tabs) of Nordette this Mar. 22, 3pm and will take the 2nd dose of another 4 tabs this 3am. Upon our computation, she's suppose to start her period yesterdat, mar. 21. Did we miss something in the calculation? I am worried on the accident yester day but I am more worried on her delayed onset of period. What is the time frame we must wait after the last dose of Nordette to take effect (start of her mens) ?