HELP! 7w5d yolk sac but no baby!

Im 7w5d (according to my LMP) today I had a sonogram done. She saw a yolk sac but no baby. My SO said maybe I’m behind but considering when we had sex and AF due date, I couldn’t be less than 6w5d. Shouldn’t I have been able to see something!? I’m feeling very sad and disappointed. We were so happy to see the baby today and to hear there’s only a yolk sac made me want to cry. Did this happen to anyone else and they continued to have a healthy pregnancy or should I be waiting to miscarry? I’ve had light cramping on and off since AF DD and no bleeding at all.

Help! 😩😩😩