I am so sorry for your loss (((hug)))
I did have a miscarriage. But were not discouraged. We will try again :)
This happens more often than you would think and it can mean one of two things...1) the pregnancy may not be viable OR (the more common one) you due date according to LMP does not match the actual age of your baby:
Gestational age based upon your last menstrual period (LMP) is based on the assumption that a woman’s cycle is 28 days and she ovulates on Day 14. The thing is, most women don’t follow this pattern and sometimes it is WAY off. If you ovulated later than Day 14, your baby is not as old as your LMP suggests.
Your doctor is doing the right thing by drawing your blood. He/she is testing to see how much your hCG levels increase. In a viable pregnancy, they double about every 48 hours. Often, a doctor will also do another unltrasound in a week or two to compare the two ultrasounds.
Please know that the majority of posts I've seen about this, the 2nd scenario is the most frequent outcome...You will be in my prayers!