Hi the heart beat should come anywhere between 6 to 8 weeks, See there are 2 reasons for no heart beat / no sac 1. Late conception, if your ovulation is delayed say instead of 14th day it happend on 20th day then its called late conception. So your LMP weeks and scan weeks would not match. If that's the case then heart beat should come within a week. 2 . The second reason is missed abortion, due to chromosomal abnormalities the fetus did not survive. So please wait till your next scan, As of now we can't confirm.

It was gestational sac and small yolk sac which was shown up in scan with age less than 4 weeks... I just saw doctor reports

Let's hope for the best.. Please be positive ..after two weeks you will get to know .. if any discharge by any chance just report to your doctor immediately.. Tc