What Causes Delayed Period While Having PCOD?

I have done laproscopy on Oct 28.I have pcod.after that I didnt haven t get periods.i have taken novelon tablets from december 30. Last tablet was on Jan 19.waited for 1 week.no periods.then started taking sysron for 5 days,3 times from Jan 28.still no periods.i m ttc for last 4 years