Hi I dont want to worry you, this may be long (and the chances of this happening are apparently 1 in 48,000 or something! gosh I'm unlucky) but last year I found out I was pregnant and had severe groin area pain one morning 2 days after the BFP that there was no way around other than a trip to A and E. I was scanned for an ectopic which wasnt found and a gestational sac measuring nearly 6 weeks was found in my uterus, they said it was ok for dates and I had another scan for 2 weeks time to see if the pregnancy progressed.
The pain was still coming and going at any time it pleased and was so bad I had to take FIL's painkillers (hes an opiate addict so they are strong!) and the uterine pregnancy hadnt progressed at the next scan. I was gutted and at the time thought I'd just miscarried. They scanned the painful area yet again (the same sonographer as first time) and couldnt find any ectopic either despite my pain persisting.
It was only when I was referred to a specialist EPU miles away after they found my HCG was too high for the uterine pregnancy to have been the only one and scanned by someone who knew what they were doing that they found the ectopic. This was after weeks and 2 scans specifically checking for one and I was furious! I could have died and they didnt find what was there that they were looking for in the first place!
Sorry I might have rambled a lot here! But the thing is that even when there is a problem sometimes they don't pick it up (i lost my trust with the whole scan deal after this), but the uterine pregnancy of mine only failed because of the ectopic, and its very likely you are measuring fine for dates. Not much can be seen at such an early stage. Have you been offered a follow up scan in a week or 2 to find out if the pregnancy is progressing?
I would try not to worry though its easier said than done! I found out I was pregnant again just before NYE and didnt even consider myself pregnant despite horrendous symptoms till my 12 week scan, I felt awful and in limbo full of anxiety everyday waiting, and there I was utterly shocked to see the baby in its full glory! Even now though I am worrying again about second trimester miscarriage, genetic disorders heart defects etc
Its normal to never feel completely safe after a m/c or bad experience but from what you say everything seems normal, its unlikely youll see more than a sac at this stage. Now I know why they dont do early scans usually as seeing nothing but a sac is not very convincing, it wasnt really for me when I saw the uterine sac when I had the ectopic.
Wishing you lots of luck and hope your feeling a bit better, sorry for the rambling! xxx