my first pregnancy after one miscarriage

Julie • |16| Mommy to be😊❤️ January 2k18
I had an ultrasound back in June... OB said I was messuring 4 weeks but I was 8 weeks 1 day any advice on this? Should I be concerned for my baby's health other than that heartbeat was at 160 beats per minute everything looked fine they said. I will be 12 weeks Monday.