Pregnant, Bleeding, Spotting. Prescribed Duphaston, Bleeding, Back Pain. Symptoms Of Miscarriage?

My pregnancy tests were all positive..but suddenly i started having blood spots..went for an a ultrasound ...it showed an empty cas..I m suppose to be 8 weeks now..my doctor prescribed duphaston 19mg twice a day..but I m having blood every time I go to the bathroom plus cramps as if I m on my Pms plus Back pain..am I having a misscarriage? If so, can I stop using the medicine?