They said they are certain now that there is a small sac in my womb but they cannot be certain as they can't see anything inside yet. Is that normal for 5 weeks pregnant? My hcg is doubling every 48hours anyone else experience this? I had a scan last Thursday and on Tuesday gone and they seen a small uncertain sac but they were not sure it was a sac. I'm a mess with worry :'( I am exactly 5 weeks pregnant today. My hcg was 640 on monday