Hello, I am 19, 98 lbs. at 5'3". I am usually underweight, it can't be helped. My period has been irregular from my menarche when I was 13. I am sexually active, but not pregnant - I have taken more than 3 pregnancy tests in the span of 2 months which all turned out negative. I have also had an transvaginal ultrasound done as well, which showed I am not pregnant. This also showed me that I have polycystic ovaries and a retroverted uterus. I haven't gotten my period for 3 months now so my doctor put me on a 10 day Provera challenge, I'm on my 9th day and I still haven't gotten it yet. Should I wait a few days before going back to the doctor and getting a new prescription? Or should I immediately go back and continue until my period comes? How long does one's period come, usually, after the last pill of the 10 pack of Provera? Please answer specifically and as detailed as possible. Thank you.