Easy ultrasound measuring behind

Had an ultrasound on 2/21. I would have been 8 weeks and 4 days. There was a heartbeat and i believe I saw the bpm were between 150 and 170. There was still a yolk sac. When measuring the baby and the sac it appeared to be 7 weeks 3 days and 7 weeks 6 days.

Is it normal to measure a week behind at an early ultrasound?

My daughter who is now one was measuring behind later in the pregnancy and she had a single umbilical artery so I saw a growth specialist quite often with her.

Do you think that’ll be the case now? I had some brown spotting last night and a little cramping but yesterday I was beyond stressed and crying all day due to personal issues.

Please help or I’m going to drive myself crazy.