A. --- I hope this is helpful information, but your situation sounds very similar to the beginnings of my 1st two pregnancies which resulted in unviable (and even dangerous) situations. THE first most critical is the potential for ectopic pregancy (when the fertilized egg develops INSIDE the TINY felopian tubes) - This can BE VERY DANGEROUS FOR YOU!!! My HCG levels were increasing, yet vaginal ultrasound revealed NOTHING in the womb - A more high tech ultrasound procedure of tubes, etc revealed a "bulge" in the tube that was the growing egg!!! A quick surgical removed the egg and SAVED MY TUBE!!! Secondly, I have endured a molar pregnancy -- once again HCG levels were increasing VERY RAPIDLY, yet this time the ultrasound revealed a cluster of cells that were non viable in the uterus --- safely removed with D & C. FINALLY, HOPE!!! The first ultrasound with my BEAUTIFUL baby girl DID NOT reveal anything in the womb - I was devastated!!! and was sent home to AWAIT MY MISSED ABORTION!!! When I came back in 1 week to check levels, etc...another ultrasound was done and THERE WAS MY BABY's BEAUTIFUL HEART BEAT!!! Therefore, I caution you that it could be something serious or your little one might be taking its time to develop like I believe mine did~!!!
Take care.,..would love to find out what you discover!!!