No fetal pole, gestational sac — need opinions

So I went for an ultrasound. Based off my last period I’d be about 5 weeks 5 days.. ish. I was alarmed to find out that they think my gestational sac/yolk sac measured at about 6 weeks 4 days and I had no fetal pole. Which I know is something to be concerned over. If I was 6 weeks 4 days, that puts me pregnant almost a week before the first day of my last period. They want me to come back in for another ultrasound next week but now I’m just so discouraged that this isn’t a viable pregnancy..