has any one else ever been 5wks 5 days and just been able to see the sac no yolk yet?

My doctor told me not to worry but I can't help it I've had two miss carriages in the past and now I am 5 wks and 5 days and I had my scan done the doctor could only see the sac but she said she could also see a shadow of what she is pretty sure is the baby growing I'm just to early to see more on the ultra sound. Has anyone else ever had this? I'm just nervous I go back on march 22nd to recheck with another ultra sound I just want my little baby to be healthy so bad!!