9W 5D by LMP but US only shows 6 Weeks

This is my first pregnancy which took two years to concieve (conceive). My LMP was May 8 but on my first Vaginal Ultrasound yesterday only measured 6 weeks with no heartbeat which by my LMP should be 9 weeks 5 days. She asked if I could be off on my dates and I said no I remember my period. I took my first pregnancy test June 5 which was positive. I had an HCG drawn June 7 which was 72. I work at the hospital and did an US for fun June 11 which showed no sac just my uterus. The US tech said you must not be  four weeks yet which I should have been 5 weeks.  Did another US June 23 finally a gestational sac but no yolk sac. My sac only measured five weeks.  July 1st another US finally showed a yolk sac but no fetal pole. Sac measured about six weeks. On July 15 Vaginal US showed fetal pole at about six weeks but no heartbeat. My question is my sac has not grown in alomost two weeks but whats inside has developed to a fetal pole. Has anyone every had this happen. Could I be off on my dates that much? My doctor said that if Im sure about my dates then Im miscarried at 6 weeks and for whatever reason stopped growning them but said its strange that I have not had bleeding or cramping and still very tired and nauseated and my boobs still hurt off and on. She said to come back in 5 days to double check before we do a D&C. My HCG level yesterday was 43146 and I will have another on monday. Some of me thinks that baby didnt  develop right from the beginning and that is what happended and a big part of me hopes and prays I am way of on my dates but I dont understand why the sac isnt growing. She also said it could be a Molar Pregnancy too but we would have to wait and see. Has anyone had this happen???? I am devasted and would like to know sililar stories regardless of the outcome.

[EmM76]

I had my first ultrasound of what I believe I was 8weeks and 3days based on my lmp. The ultrasound showed an empty gestational sac of 7weeks and 2days. i had HCG test and came out good as the doctor said that my pregnancy is progressing. After two weeks i had another abdominal ultrasound and still it was empty and the gestational sac age went to 6weeks 3day.How could this happen?  Had another blood test and waiting for the result. Im worried and scared... the doctor said it was a failed pregnancy. I dont know what to think... any advise...