Hello
Thanks for your query.
At 5 - 6 weeks 
pregnancy, the 
yolk sac and 
gestational sac is seen.
After 6 weeks, fetal tissue should be seen also.
So you will completely have the clear picture , after your 
ultrasound after one week.
Also, if the sac is flattened, that is because of a condition called SCH ( sub chorionic hemorrhage ), that is, bleeding present within the 
uterus, in the tissue that supports the pregnancy.
Hence, the future for such a pregnancy is guarded.
If you are lucky, the bleed might stop, and the pregnancy might continue normally, or if it has affected the developing pregnancy significantly, you would know it within a week.
Meanwhile, continue taking the medications as prescribed, take adequate rest, avoid exertion and sexual activity.
All the best.