First ultrasound

So according to my last period and glow in should be 7 weeks 2 days but I had my first ultrasound today and she said I look to be around 5 and a half weeks and there was no baby visable yet. She said there was a yolk sac and definitely a pregnancy but that I seemed earlier on. I'm nervous and scared. I pray there is a little bean in there! I go back in two weeks for another ultrasound and I hope I can see the baby and the heartbeat. The tech didn't seem worried or anything but I can't help but be. Any similar situation out there??