I was physically active without protection and took unwanted 72 immediately , my periods date was 23rd and still I haven't got periods , I took a urine pregnancy test and it's shows negative , I always get periods on time means they are regular just sometimes 2-3 dYs delay , also I had taken unwanted 72 on 1st of January and I got little bleeding on 14th of Jan bleeding light and not lasting even for a day I feel dull pain lower abdomen like periods will come but it's not happening , what can this be due to , should I take regestrone to get my periods?