Please answer my question..

I've just found out I was pregnant, I went for a scan and they said I was still too early, around 5 weeks. There was a sac but nothing so they calculated me at around 5 weeks. I have to have early scans as I've previously has a miscarriage and an eptopic. So the reason for me having an early scan was to check the my tubes were clear. So far everything looks good, my hcg is 1220 and I'm awaiting my 2 lot of bloods to come back to my midwife. I had my scan 2 days ago. Is it normal to see a empty sac at 5 weeks? I'm a little upset. Please help.