Is It Safe To Take Miprogen 400 ?

My LMP was 27 oct. I had slight bleeding on 24th Jan eve and maybe half a pad and then stopped after a few hours. I asked my doc n she suggested susten 200 for 7 days, morning and night. Then on 7th feb in the night again i started bleeding, a few clots n some dark blood which stopped by midnight. The next day i took a usg which did not show any chorionic bleeding in the uterus. However i have 3 fibroids, sub serous, the largest being abt 7x5 cm. The others abt 4x3 cm. The cervix is 3.1 cm. The doc advised miprogen 400 for 20 days vaginally once a day. What could be the cause of bleeding as report shows everything is fine. Worried. Pls help me understand. What cares do i need to take. Im taking rest. The miprogen is giving me headache and nausea which i didn t have previously. Are there any side effects to miptogen