What Causes A Delayed Period With Negative Pregnancy Test?

i am suffering from PCOS. I was taking krimson 35 but have stopped it a month ago. I got my last period on 8th oct, then stopped taking krimson. after 40 days i took meprate for 5 days. its been 2 weeks now since taking meprate but i didnt get my periods. pregnancy test was negative. please help..what cud be the reason