TTC, Just quit taking BC, I'm late-Help!?

I have been taking birth control for a little over 2 yrs (ogestral .05). I had my last pill in the beginning of Aug and started my per. for that month also had Sept. per., both were right on track. I am now 11 days late for the month of Oct.(had a little spotting on two different days, enough for pant. lin.). I have taken preg. tests and they are Neg. Is my per. late and spotty because it is trying to get back to normal or what?