They want to do a d&c to get the rest of the tissue out of you. I had one in february. Im so sorry for your loss. I was nine and a half weeks and knew for seven of those weeks. Take care girl and good luck from AL.
I agree with the poster above. I had a very similar experience with my first miscarriage. It is what is called an incomplete miscarriage, and leaving product of conception in the uterus can cause complications. In my case it caused dangerously heavy bleeding and resulted in an emergency d&c.
If there is still tissue there, chances are this is not your period that has started, but is in actual fact your body attempting to rid itself of the remaining tissue. If the bleeding gets heavy (a pad an hour), you must seek emergency medical treatment. In the meantime, please ensure you are following up with your Dr. It's important. All the best to you.
You should insist on having another ultrasound after period to see whether your body has expelled it all.If not then D&C is the best option to clean up sothat you dont face complication in next pregnancy due to old tissues from previous pregnancy.
I hope it helps.