Cannot see embryo at 6 weeks

Hi all, this is my second time getting a BFP (previous time had a chemical pregnancy miscarriage).. And my happiness became shortlived when the gynae could not see the embryo within the gestational sac during the transvaginal scan. I'm at 6weeks pregnancy and will need to go back a week later for another scan. Anyone had a similar experience but went on to have a smooth sailing pregnancy? Am so worried that this will be another disappointing miscarriage :(