What Causes Delayed Periods Post Intake Of Trust Pills?

Hi. I had unprotected sex last dec16 and took 4 trust pills that same night, 9pm. And another 4 the following day dec17 9pm. I forgot it was supposed to be taken at 12hr interval so I took another 4, dec18, 8pm and then 4 more dec19 8am. My last period was nov16, and ended nov 20 I think. And btw, i get irregular periods all the time. Today its dec 25 and still havent got my period. I was supposed to get my period somewhere mid this month or 3rd week. I took a pt test just now but tested negative. It was my 4th pt since dec16. Am I pregnant? Should I be worried? Please help. Thank you