Yeah might have ovulated at a different time. From my last period till I seen the Dr I would have been 12wks but I was only 7, so it's very possible to be off
My period was way of about 18 days n i was almost two weeks pregnant by the ultrasound but if we went by my period i would be a month or so just it pretty messed up at times...
When I found out I was prego with this baby I went to the hospital for pains and they said I was like only a week pregnant. But when I went for blood work I was about 3 weeks. And hen I went to the doctor I was right at about 4 weeks. So it's hard to tell.
Same thing happened to me, I had an US around the same time and they didn't see a heartbeat or fetus, and said I was further behind than my LMP indicated. I'm now 18 wks and baby's fine and doing well. Its just early on in development.
My period date and ultrasound measurement was off by 9 days. So my due date is may 17th instead of the 8th :-( but that's ok and normal from what I have seen.