Why Is Dianette Not Causing Withdrawal Bleeding?

I have been taking Dianette for pcos along with metformin. I am on my 7 day break from the pill its day 5 and have not recieved any withdrawal bleed. Is this normal? Its my first month on dianette and started it without having any previous period because of my PCOS as I only menstrate every few years, I had sex the month previous however.