Question with early pregnancy?

I'am 7 weeks and 5 days gestational age pregnant, and i went to the obgyn to have the first ultrasound done, and all the could see is the gestational sac and the yolk sac, is this normal? she told me to come back in a week to have a nother one done. she also said the fetal age was about 5 and a half weeks. i just dont know what to think, please help so i can stop worring. maybe its to early to see the baby.