Sac but no baby on ultrasound

I had my first ultrasound today was told 8w3d. The image showed a sac but no baby. The US tech said the sac was measuring 5 weeks and not 8 so it is possible that the baby is not visible yet OR “something is wrong.” I got a blood draw and was instructed to make an appointment for repeat US in 10 days. Searching for some positivity, my husband and I had been trying for 3 years. My doctor will be calling me today with some more information. Any input is greatly appreciated!💓💓💓