What Causes Blood In Uterus During Pregnancy?

I have PCOS finally got pregnant in January. Everyting was progressing then I went for my ultrasound. There was a small sac and my uterus had blood in it. My hcg was 850 and went to 1200 (mon-mon). He said I would probably miscarry but it has been a week and I have no signs of anything happening. I am going crazy. Any suggestions?