thanks for your query.
I guess they would be doing another ultrasound
, but please request for a transvaginal scan, not an abdominal one.
They would not ask you to fast that way, unless they are planning some procedure , like a termination as they think the pregnancy
is non viable.
A pregnancy is non viable if the gestational sac
exceeds 20 mm without visualization of an embryo.
Irregular collapsing sac also indicates an abortion
On a transvaginal scan, if the sac is more than 20 mm without embryo after 6 weeks, it is most definitely non viable pregnancy.
Please have repeat scan, transvaginal and then consult your doctor