Question about my period...

Margaret
I could easily contact my doctor, but I feel like I'd like to hear from other ladies who may have experienced the same thing. 
I'm on my placebo pills - four pills in - and have yet to have my period kick in. It usually occurs by the second placebo pill. I've taken a handful of pregnancy tests already - not pregnant. 
So my question is this: have you ever just not had your period even though you took the placebo pills? 
THANK YOU!!