period. pill. paranoid.

I'm on my second pill blister pack (first time on the pill). I had an issue with have my period for 2 months with a different pill. My period stopped on the placebo pills on the first blister pack. I had unprotected sex last week, and I've taken 2 days of placebo pills (on the second blister pack) and no period yet? On average how many placebo pills are you on before your period starts? I'm a very paranoid person and I'm anxious I may be pregnant.