Hello and Welcome to ‘Ask A Doctor’ service. I have reviewed your query and here is my advice.
I can understand your concern.
Usually by 6 weeks of
gestational age,
gestational sac can be seen in trans abdominal
ultrasound and fetal heart can be seen by around 7 weeks.
As your ultrasound showing 6 weeks only, there is possibility of wrong dates sometimes.
In that case, you better to wait for one week to ten days and repeat the ultrasound.
In case of wrong dates, by that time at least
fetal pole can be seen.
If fetal pole is also absent by that time, there is possibility of of
blighted ovum, means development of empty gestational sac without fetus.
So, please go for repeat ultrasound examination as explained with your doctor's advice and proceed accordingly.
Hope I have answered your question and I will be happy to answer any further follow up questions.
Take care.