M. O,
Waiting is the worst part. I am sorry you have to go through this. My third pregnancy was a blighted ovum and unfortunately it sounds somewhat like what you described. I am surprized your doctor didn't mention it. That means that a fertilized egg makes it to the uterus and your body is technically pregnant. A sac is made, a placenta grows, you can even start to show a little. But the fertilized egg never turns into an embryo, it just gets absorbed back into the body so you have an empty sac. After the doctor is sure there is no baby, the mother can wait until she naturally miscarries or she can have a DNC. My doctor said as soon as I started bleeding, I could go to the hospital and have one if I wanted.
The happy news was I was able to get pregnant quickly after my DNC and had two more healthy children. 3 of my 4 kids started embryonic life as twins, and although it is always disappointing to lose one, I am so grateful for the healthy ones I have been blessed with.
If this is an ectopic pregnancy, treating it early gives you the best chance at a healthy pregnancy later on. I hope you just have an embryo that's good at hiding, but if not, I wish you the best in the future.
S.