Please help

[Shruri]

Had first done my scan at 26 Dec 2016 when i got to know that  i am pregnant. That time we could only see gestational sac. After one week again i went to see one more doctor. She said do a scan after 7 days. I did a scan on
16th Jan 2017. There we could see gestational sac 1.6 cm and yolk sac 2.5 mm but no heartbeat. As per LMP i was 7weeks 4 days pregnant but as per gestational sac size i was 6 weeks. Doctor said we might have to terminate the baby as no heartbeat is there. By this tiem we would have got the heartbeat. So, for second opinion she had sent to sm other doctor. She said we can wait for one more week to see if heartbeat comes. can anyone tell after yolk sac comes after how many days heartbeat will come. I have to go for a scan on 21th jan. This time going to a radiologist for a scan. If still heartbeat does not come, i might have to terminate pregnancy. Plz suggest what should i do.