What Can Cause Delay In Periods?

hi sir, i got married recently of aug 2010. For that i took a pills PRIMOLUT-N to skip. bleeding occurs after 10 days from regular date.(due date sep 3rd)on october 5th (due date) . Then for some reason took again the same pills on november , due date 14th. till date i dont have any symptoms for mensturation. we,ve planned for pregnency form november and also started for that, but the result is negative. what is the reason and solution? kindly do for me