What Causes Missed Periods Post Intake Of Regestrone?

Hi doctor. I got married in nov 2014. I have pcos. Got my last periods on dec 29 2014 and still dint get periods. The preg urine test came out to be negative. So doc gave me regestrone twice a day for 5 days.i already took 8 tabs and stil dint get periods. I m afraid if i m pregnant. Wil regestrone causes miscarriage. Is urine test is not sufficient to confirm pregnancy for ppl with pcos .