What Causes Delayed Period While On Yasmin?

I took eight Yasmin pills as EC, 3 to start, then another 2 and another 3, on 13th of March after having protected sex but then the condom broke and I had my last period on 12 February, so I was expecting it round about the same time. I want to know if there is a possibility of me being pregnant. It s been 3 days and my period hasn t come yet and I am starting to worry.