Feeling less then

So I went in for my first prenatal appointment today and I found out that my yolk sac was too big for me being 6 weeks and 2 days so it is possible that my pregnancy won't progress so far my HGC levels are going down. I won't know anything until next week until another ultrasound. I am trying to keep positive but I've already had a stillbirth and now I might have to add miscarriage to. Has anybody ever had their sack be too big for the weeks in pregnancy that they are? If that makes any sense to anyone.