I've Been On Levlen Ed For The Past 2 Years.

I've been on Levlen ed for the past 2 years. I'm on the last day of my sugar pill, and still haven't got my period. I did do a pregnancy test yesterday, which came out negative.
Should I start my active pills tomorrow even if I haven't got my period? And what could be the reason behind this? (It's never happened before. I usually begin bleeding on day 3-4 of my sugar pills)