I'm really glad that you waited. You are still really early in your pregnancy that some numbers could have just been off which could be why you didn't see anything in your first u/s.
I was 6w2d when all we found was an empty sac. I happened to be moving states the very next day and also leaving the country for a week. My RE said that normal procedure would be to have a follow-up u/s in a week but considering my circumstances that was not possible. He advised that it was probably a blighted ovum (which it was) but if I had not naturally miscarried by the time I was back in the States to request an u/s on the day of my consult with the new RE (which was scheduled for when we returned). I ended up miscarrying naturally, but if my first RE would have prescribed anything to help the m/c along but the fetus was just behind.. that could have been terrible.
I am so glad that things worked out for you! Lots of luck in your pregnancy!