You can ask for an U/S from your GP at ANY time! I have, I was concerned about the lack of visuals we got at our 12 wk scan so we had a 14 wk scan too. I also asked for what I called a "dating" scan at 7 wks, but in all honesty it was because I was concerned. As it turned out I started bleeding (all turned out fine as you can see ) and ended up needing the 7 wk scan anyway. So my suggestion is if you are concerned, go have a scan.

At 6 weeks sometimes you can see the heartbeat but its generally definite at 7 wks. So if they can't see one they'll probably tell you to come back in a week, and if they don't I'd request it (but thats just me). Some places allow you to hear the heartbeat (we got to hear it at 6wks 3days) but it depends on the equiptment and the sonographer. Other than that I'd say its just a little blob on the screen, can't give you much more detail than that. Its ok to worry, and to want to be sure and I think its alot better to have a scan and put your mind at ease than to worry yourself sick over it iykwim.

Goodluck! And if your GP isn't helpful see another Its your right as a patient to request an U/S.

*hugs*
Cailin