if you`ve had a late ovulation you might think you`re 7 weeks pregnant but you are less.
There is a difference between counting weeks p.m. or p.c.
p.m is counting from the last period (post menstruation
p.c. is counting from the conception - when you actually got pregnant ( post conception) which is always 2 weeks less.
Usually when there is a yolk sac
- there is an embryo.
The embryo appears on the edge of the yolk sac - in whole it looks like a ring - with the embryo lying on one side of the yolk sac. It sometimes is so small it`s hard to detect it at an early stage. especially if it`s close to the wall.
I would check the scan again in 1-2 weeks. I would also check the beta HCG
leverls if they are going up nicely.
Do you mean you have had 3 previous pregnancies - with no embryo developing?
If this is the case you should be checked for genetic disorders or blood disorders ( such as MTHFR or other thrombo-embolic disorders that could cause problems in the development of early pregnancy
Hope this helps,