I don't know about your Ob but mine told me as long as the numbers keep doubling every 48 hours you are gravy. Hcg levels are supposed to go up each day. If they are then your baby is developing. I went in for my 8 week visit on monday and they could see my baby and hear its heartbeat, but the baby was 6 weeks and 4 days old.And they went in vaginally too. That makes a huge difference. Now it is 7 weeks and 3 days old. Don't worry about not being able to see it yet. Just enjoy and watch your numbers grow. You'll be able to see your baby soon enough.
I had 6w1d us and doc said it was too early. Some women get lucky and can see more at that point or even before but RE assured me that 7 weeks was a far better time to check for baby and heartbeat. My beta went from 600 to 2000 and at 6 weeks was at 17000. Totally fine. Numbers vary a great deal. All you need to worry about is that YOUR numbers are doubling. If they are, you're on your way. It's hard not to compare your pregnancy to others' but you have to trust your RE. if there were reason for concern, he/she would tell you.
Good luck!
I am not sure about numbers or anything. I just had an ultra sound done at 4 weeks and 5 days (had to go early because I am high risk) the only think we could see was a little white "bean" ...we were just checking to see where it implanted. What kind of u/s did you get? Sorry I am not more help...