Has anyone been in a similar situation?

Had a scan at 6weeks from LMP but all they saw was a 5mm GS and told me to come back in a week. They thought I was possibly 4.5 to 5 weeks going by how small it was in size.

Went back yest at possibly 5.5-6 weeks and the sac had increased in size slightly but still nothing in it. They seemed positive that there was some progress.They've asked me to go back in 2 weeks for the final deciding scan. Has anyone had this where their dates had been hugely off due to a randomly very late ovulation/implantation and everything ended up being ok?! I've had a MMC before and it's like a recurring nightmare :-(