Threatened miscarriage- need reassurance.

Has anyone ever had this happen and had a good outcome?
I have 2 children to a previous relationship and recently I found out I was pregnant with my fiancées first. Thing were great we were so excited, then on Thursday I had a massive bleed (tmi) but it was very very heavy. I went straight to the doc and was sent for a scan. I should be 6 weeks, but the sac was measuring at 5w 5 days. Not that far off I was ok, but they couldn't see anything inside the sac. I had a blood test Thursday and my hcg levels look good, but the doc wanted another blood test to see if the hcg levels are rising. So I'll find out Monday. But I'm so worried. I've had a little spotting since but very little.
I've had 2 miscarriages before but they were very different and the scan showed nothing and hcg levels went down straight away.
So I'm just wondering if anyone else has had something similar and had a continuing pregnancy?
Thanks.