5 weeks and 6 days ultrasound! is it normal?

Today I had a scan (vaginal) they told me I was 5 weeks and 6 days so almost 6 weeks but they did not see anything besides the sac and if I did not misunderstud the yolk sac. They told me is normal not to see anything at this moment but I cant help to be worried . First time pregnant for me!  Your experiences?? Think its normal??