I had bleeding at 5wks, 1 day and it was bright red. Went for a scan and all they could see was the yolk sac and yolk. Went back 11 days later and everything was fine. I cant say about being a week behind, but if the sonographer is even out by 1mm on a scan when measuring it can mean the difference between being 1 week ahead or 1 week behind. I think the heart starts beating between weeks 6 and 7 (you could have only missed out by a day or so!!!). When I went back at 6 weeks, 5 days the heart had only just started beating apparently - 120bpm. Hope you get some answers soon and just wanted to send you some big hugs