hi I am a 27 year old woman, my partner and I decided to start trying for a baby 4 months ago. I was on yasmin for the past 5 years, but stopped taking it 13th of june 2011. I have had no period and no signs of a period comming since my withdrawal bleed. I have done several pregnancy tests all of which have been negative. I am very concerned. How common is this? and how long should I leave it before i go to the doctors?