What Can Cause Delay In Periods?

hello im writing because i haven't had a period in what will be 3 months the end of this month and i want to know what might be causing it? my last period was in november and lasted pretty much the whole month on and off. it only stopped a few times for about a day each time but not a full day. i went to my doctor about it when the bleeding didnt stop and she prescibed orthocyclen to make the bleeding stop. i have the ortho cyclen but i didnt use them because the bleeding stopped on its own after a while and also my fiance and i have been trying to have a baby for some time. after the bleeding stopped i havent had a period yet for the whole of december and january and the whole of this month