Does Intake Of Primolut N Help Regularise Periods?

Hi, I last had my periods on 12th feb, 2015. technically they should have begun by 15th March however i am not yet down. I visited a gynaec and she prescribed Primolut N to me. However while reading about it on the internet I figured it is meant for delaying periods. when am I likely to get down? Should I get an ultra sound? I had protected intercourse between 22nd-28feb.