no yolk sac or fetal pole

Hey guys. I went for an USS when I was 6 weeks from LMP. They only saw a 5mm gest sac with neither a yolk sac nor a fetal pole and said I was maybe 4.5 to 5 weeks not 6. went back today at 7weeks from my LMP but a week after the previous USS (?5 to 6 weeks?) and the GS has grown to 8.5mm but still no yolk sac or fetal pole. they've asked me to go back for a rescan im 2 weeks. I'm feeling very ominous about it as ive had a previous mmc. anyone had this situation and turned out to be ok? or has it ended in mc or a blighted ovum? thanks in advance for replies :)