Hcg high but not doubling

Shannon

On April 16 hcg was 44800 (6w)

On April 20 79000 (6+4)

I had spotting from the 12th-18th

Ultrasound on April 14 (5+5) showed yolk sac only

Just looking if anyone had similar experience. I’ve already been told this pregnancy is most definitely not viable.