My experience with Medroxyprogesterone (Progestin)

My doctor prescribed me medroxyprogesterone to start my period. It’s been about a week and still no period. I’ve had some pinkish/brown discharge twice but that’s it so far. I don’t know if I should keep waiting or call my doctor. My body’s been feeling like I’m going to get it because my lower back has been killing me these past two weeks and I’ve been emotional. Im getting stressed because I need to get this period so I can get a pelvic ultrasound to see if I can have children. If you’ve had an experience with it please let me know how it worked for you. TIA.