2 early US- measuring 5w 2d and 10 days later 5 w 5d and only a gestational sac

My LMP was 7/15 and I had a transabdominal scan 8/20 and sac measured 5 w 2 d. 10 days later had a transabdominal scan followed by a vaginal scan and the gestational sac measured 5 w 5 d. No fetus or heartbeat. Doctor was not very optimistic that things are ok. I've had two miscarriages in the past 9 months and 4 in total with 2 live births. I'm 41 this time around and am concerned that something has changed. I am on supplemental progesterone as when I miscarried in April my pg was 1.5 at 4.5 weeks pregnant. I am waiting to hear what my hcg levels are and should know tomorrow afternoon. I have no pg symptoms other than being tired but didn't have with my son born in 2011 either. I have had no spotting or heavy cramping- just tired. Is it possible that things are ok just scanned too early? I would love to have another child and for my son to not be an only child (my other son is 22) I may have ovulated a week later than the 14th day. Thanks for your input.