Heartbeat query, I'm nervous

I'm hoping people can share their experiences because I'm so nervous right now!

Two weeks ago I had a pelvic scan and measured 6w 3d but there was no heartbeat. The sonographer was convinced it was all over and I was devastated. My Dr didn't agree, saying we're still in the margin for error. I have another scan tomorrow, so in theory should be 8w+.

Has anyone else experienced this? Did you see a heartbeat at 8 weeks?

I have a long history of severe endo and this is my third pregnancy. Hoping for a rainbow baby. 🤞🤞