Welcome to HCM,
I will try my best to provide you with best possible professional recommendations to your questions.
There will be some disparity in LMP and USG in assessing the gestational age
As there in no definite sac development, its called as blighted ovum
, there are less chances of continuation of pregnancy
Yo can wait for one more week and get a scan done to see if there is any regular sac developed, you can discuss with your doctor regarding the risks of continuation of pregnancy.