Hi,
this happened to me. I was 12 weeks and so happy...when i found out it was a yolk sac only. Initial ultrasounds at week 5 showed there was no tadpole, but the DR said it must have just been too small to see. It is called a blighted ovum: somehow when the egg meets the sperm either one of them is not prepared, or as in my case, my husband's sperm passed the 72-hr period it is able to stay alive in the environment in a woman's womb; so even though conception happened, it was faulty.
it was a very sad and shocking time. When our midwife called to explained I needed a D&C i could not go ahead with it. The Yolk sac continued to grow along with my hormone levels, even though i knew i wasn't technically pregnant, yet i still felt every symptom a normally pregnant woman should feel. The strangest thing was that when instead of a very expensive D&C my husband and I opted to see an abortion clinic to help terminate a baby-less pregnancy...we confirmed there was no embryo, and received the at home tissue expelling drug, I had the symptoms of giving birth: to blood clots.
it was very difficult. even though i went through it, with the time that has passed thankfully my memory of it has faded a bit. now, long months later, I am finally expecting. it has been a long and painful process. I know it's possible to get through it, be it as hard as it is. If you need someone to talk to, I am here for you.