6 week sono with a shadow

Okay I had my sono today I'm measuring 6 weeks. (Had a MC recently so my dates are hard to determine) The dr said it's hard to tell but there was a very faint shadow that (to me & husband) looks like the start of the yolk sac. He also said that it's possibly the start of the yolk sac but too hard/early to tell. I have to go back in 1 week to confirm the pregnancies viability. Anybody experienced something similar? Thanks hoping for my rainbow 🌈