What Causes Delayed Period While On Cerazette?

I took Ellaone last thursday and have still had no sign of my peirod, i'm getting really really worried. I have been continuing to take my pill and drinking pennyroyal tea but nothing. I had missed 3 pills in the week before having sex took a pill on the friday and on the saturday and had sex in the early hours of sunday morning(I'm on cerazette)