What Causes Delayed Periods And Nausea After Taking I-pill?

Hi... I am 29 year old female married 4 months ago. I had my last period on 10th July and had inter course on 28th July. Since the condom tore off, I took an ipill within 12 hours. During our second intercourse on 29th, the condom tore again... But this time I didn t take an ipill... My periods were expected on 8th august... But it is not yet happened.. I experience severe nausea... Is this because the ipill has failed and I m pregnant or it is the side effects of ipill ?