Hi ,i Took 4 Pills Of Meprate (4 Days Each

Hi ,i took 4 pills of meprate (4 days each 1) and waited for 4 days. i doubted its not working and took 4 more pills (total ) 8 pills. i got it.
The next month i got my periods without pills. Does this second dose of extra pills work for next month.
Can it happen like that.