I don’t know what to think

I went to my first ultrasound appointment on 12/5. According to my LMP on 10/10 I was supposed to be exactly 8 weeks, but my OB did an ultrasound and EGA is 6 weeks 4 days. I was confused but my OB keeps reassuring I just ovulate late since my history is irregular period. The baby measure at CRL .69cm, everything normal but no heart beat. She said “there is no immediate concern for viability, no heart beat detected due to early gestational age” and schedule another follow up ultrasound appointment on 12/13. I know there is nothing I can do right now, and the next appointment will be the one to confirm fetal viability. I can’t help but being a nervous wreck. Please pray for me to get through the days leading to the next appointment. I will pray for the best and prepare for the worst………