What Causes Early Menstruation After Taking Unwanted 72?

doctor i took unwanted 72 24 may 2011 after takind this medicine no proble but today 30 may 2011 period start and my last period was 8 may 2011 its too early.so pls tell me is it right for my health and it will not effect my future pregnancy this irregularity.pls suggest me any solution for these side effects

shreya 23 yrs 5feet 5inch, 40 k.g.