What Causes Delayed Periods After Discontinuing Birth Control Pills?

Hi I am malini mukherjee and was on crimson 35 and after that yasmin. But recently I stopped taking yasmin but my periods which was regular after using those medicines suddenly not appearing after my due date and I am afraid anything wrong is there and after as I presumed it was due to pregnancy I went through pregnancy test with pregcolor and the out come is negative. Is it natural to have delayed periods because of discontinuation of those medicones. Please guide me as I am going through a very bad emotional patch. I was suffering from PCOS for the last two years. I am married off recently if at all I can have a child or not. please reply