Early Pregnancy Worries

Hi all, wondering if anyone has or is experiencing the same situation.

My husband and I have been ttc for a year and a half. I had my LMP on 10/30/20 and first positive test on 11/28/20. My cycles vary from 30-34 days, and I used Mira to track ovulation (highly recommend, measures estrogen and LH levels at home), it has been very difficult to pinpoint ovulation and seems like it is all over for me. Based on my LMP I assumed I was 6w 6d. I had spotting yesterday and my doc told me to go in. The ultrasound has me measured at 5w 2d. I had a blood draw for hcg levels and get results today and repeat on Saturday. I am so nervous I am either having a brightened ovum or miscarriage. My ultrasound only showed a sac, no yolk or fetal pole, however, the doc said it could just be earlier then I thought. So nervous/scared/sad.. anyone experiencing this at first ultrasound? Has anyone experienced measuring less weeks? Doc said normal to not see yolk yet, but feel like I should be further along...