Empty sac?

Ivy • 26 🌿, mama of angel babies 👼🏽👼🏽👼🏽 with a sweet girl due July 2024 💕

Had my appt today, she decided to do a tummy ultrasound and all she found was a sac. Not sure yet if it’s an empty sac or if I thought I was further along then I am but I tested positive around what I thought was 4 weeks. So I imagine I have an empty sac. Has anyone gone through this? I have to have a vaginal ultrasound tomorrow but I’m pretty sure I’ve miscarried.