Early scan. Empty sac seen.

I went to the hospital today for an early scan due to bleeding (enough to wear a pad, quite red, like a period).

We thought we was around 6/7 weeks pregnant but could be 4/5 weeks. Dr scanned me with internal scanning and seen a sac that appeared empty. I had bloods taken and got to go back in 48 hrs to see if hcg blood levels are rising.

Has any one got any success stories or is it likely I’ve miscarried? If I’ve miscarried, why is the sac still there?