Measuring a week behind in early pregnancy

Ch

I have a history of recurrent miscarriages so my dr. Scheduled me an early ultrasound today and I was supposed to be 6+2 but I was measuring at 5+2 and there was just a sac and nothing else. I’m scheduled for a repeat scan in two weeks, has anyone had this happened and it worked out fine? My numbers are also rising perfectly they have been doing blood work every few days to make sure