Are you certain of
your dates down to the day, or is it just sort of
close? I don't know if I would worry or not, if the ultrasound at 6 weeks 4 days showed two sacs, but I would begin to parse out very carefully what day my last period was and when I thought I ovulated. I hate to say anything that might be negative, especially because it could be nothing, but at 6 w 4 d or thereabouts, I'd like to see something more than a sac, or even two sacs.