I Took Postinor2 Twice In One Cycle , A Week

I took postinor2 twice in one cycle , a week apart , taking two tablet at each instance. I had my menstrual period the normal expected day on 29th day of my cycle. However I am now on my 31st day of my next cycle and I am yet to get my period , can the pills change my cycle after a normal menstruation? I also had unprotected sex on the 28th of my present cycle with the expectation of my period soonest, can I still b ovulating then? My period prior to taking postinor used to come on 28-29th day.pregnancy test shows negative.