What Causes Dark Blood Clot Discharge From Vagina During Pregnancy?

Hi, I am having 12 week of pregnancy, in last one week and half week, some complications arose. That a blood clot along with some dark colour blood bleeding, thereafter doctor ask for ultrasound, but the report suggest that every thing is normal. In last one week I am on complete bed rest, but I am having regularly dark red colour blood few drop every day, along with some transparent waterly liquid coming out. Pl. Advice.