What Causes Absence Of Periods After Taking Cyclenorm?

Hi doc..i had my last periods on 29th jan 2015..aftr dat i mised my period. i consulted my gyno on 11th march 2015 & she prescribed me to itake cyclenorm e& p. i had it and my 3 days course is course is complete. i did my pregnancy test at home which was negative.. will these tablets help for my periods and for how many days should i wait for my periods to come?