1st ultrasound

Deb

Had my 1st ultrasound today to confirm pregnancy. I should be ay 8 weeks according to my lmp date but the dr said ultrasound showed 6 weeks but the baby's heartbeat is over 100 and I'm nauseous she said were both good signs but I have to go back in a week. What happened? Ovulated late or abnormal cycle or all that? Anyone else have this happen? She told me she couldnt say for sure whether we will lose the baby or not but she said there are good signs too. Praying this nugget makes it!