I'm On My Second Month Of Taking Microgynon 20. I've

I'm on my second month of taking Microgynon 20. I've taken it everyday for the past 2 months at around the same time (in the morning). I'm on the first day of the inactive pills but my period hasn't come. I've been having menstrual cramps for the last 2 weeks. I had sex, but it was protected and I'm 18 years old. What could be wrong?