Late period?

finished my second strip of the pill on Wednesday, (28 days of pills, 7 days off) I was supposed to come on by now and I still haven't. I know I'm not pregnant as I use other types of contraception and I have no pregnancy symptoms. 
I have PCOS but I'm on the pill for this reason so I'm not overly worried about being late. But the first strip of pills I finished, only took two days after to start my period.. So why is it taking so long this time?