So very sorry :( Your doctor may do some blood tests and/or a follow up ultrasound just in case your actual ovulation/conception does not match your gestational age based on your LMP.
Sadly this is all too common. Sometimes when a pregnancy is not viable it takes the body a few weeks to figure it out. They refer to this as a missed miscarriage. Eventually your body will take care of it on it's own, or if you prefer there are other options. Talk to your Dr. I am so very very sorry for your loss and wish you peace and healing. As CHrissers said, this is not due to anything you did or did not do. It just happens sometimes.
Yes, it happened to me in 2009, at 10 weeks. There was a sac measuring at 5 weeks, 6 days but nothing else. After a few more scans over the course of 2 weeks, I miscarried naturally. During the last scan, which was 3-d, they saw another sac which they referred to as a blood sac. I did not have any bleeding and the urine test showed + for pregnancy one day before period due.
It's depressing to go through it, but I tried to believe it was for the best since it was a natural miscarriage. Sometimes these things happen because of chromosome abnormalities. I'm so sorry you are going through it.
Take care.
This happened to me at 7 weeks but it did take another 3 weeks to miscarry so I could have been in your position if I hadn't had the early scan.
I'm very sorry to hear that you are going through this. You probably can choose whether to have a d&c or wait to miscarry naturally.
Take care.