Help !!!

So I’m almost 4 weeks according to my doctor but she said she couldn’t see my yolk sac I wasn’t sure what that meant but she told me the pregnancy might be an ectopic pregnancy which means the baby is growing on my fallopian tube’s (I’m not showing any symptoms) . But then she said she could start to see the yolk sac forming just slightly but she wants me to get checked out. I left so confused and wondering if my baby if baby is OK or not ! Is it normal to see a yolk sac in the first 4 weeks ?