Birth control, why am I late?

I take Solia and I am late! this has never happened to me before, it's the 3rd day and I usually start on the 2nd day, normally this wouldn't bother me but I have nausea and the thought of cheese repulses me (and I like cheese). The chances of me being pregnant are looking pretty high right now but I wont give up just yet, does anyone know if the last week of birth control are just placebos, or if you actually have to take them to get your period, because I usually take them, but I decided to spend the night at a friends house that I haven't seen in 3 years, and like the idiot I am, I forgot the pills, I'm hoping maybe that's why I'm late? Thanks guys.