Hi!
Not sure if you are still around looking for someome to help, but thought I would share my experience.
I was at 13 weeks, going in for my first ultrasound. Very excited and ready for the heartbeat after weeks of extreme nausea and pregnancy symptoms. We got in there, and she found the gest. sac, but it was empty!! She called it a blighted ovum, and sent me up to the ER. I was crushed! She said she was suprised I had gone on for that long, since you will usually m/c these much earlier on.
Since I have had 4 more m/c, and am in the process of going through another. My doctor tells me that I too, am releasing empty eggs it appears.
Have you ever been looked at for PCOS? That is part of my problem, however I have been going untreated with it hence my continued problems. Many times with the PCOS, you produce many eggs that are not ready, but since your ovulation is so off they do not always fully form (among many other problems).

Also, have they done any genetic screening on you yet? That might help. Sometimes they can put you on some medication, and things work out. Good Luck!!