Sorry to hear this mamabear.
I had an enlarged sac which was empty and turned out to be non-viable. I was around 8 weeks going by lmp but measured 4-5 weeks. I went back for repeat scans over the next few weeks, the sac continued to grow slightly but sadly nothing ever grew inside it.
I'm sorry I don't have a more positive story for you, I'm sure others will. But I know how scary and worrying it is to be stuck in limbo and not knowing what is going on. I tried to keep myself busy between scans which helped to keep my mind off it a little.
I hope it's good news for you next week. Xxx