What Causes Delayed Period After Taking Duphaston For PCOD?

I have pcos and i am taking metformin. and the I whent to doctor and gave me duphaston. and take it 2 tablets for 10 days. Now it was 3 days after I finished taking 20 tablets but until now i dont have my period?how long do I wait to have my period?My doctor advice me to go back on my first date of my period. After my period, if we will have sex with my husband do I get pregnant already?I am hoping to have my first baby.