Thank you for putting up your problem to Healthcare Magic!
In normal intrauterine pregnancy
fetus develops cardiac activity at 6-8 weeks.
However you are having empty sac means no fetus no cardiac activity that is known as blighted ovum
In bitter but real words I would like to say that you are having failed pregnancy.
You need to start the treatment after consulting your gynecologist.
I hope this information would be both informative and helpful for you.