small sac?

stelov04

So I had an ultrasound at 8 weeks 2 days. And I am going back in thus week at 10 weeks as they think the sac around baby is quite tight/small? Anyone else experience this? I really want to see if the sac has grown more and given my baby some more room. I'm thinking just to check tomorrow. I'll be 9 weeks 6 days tomorrow... almost 10 weeks. Shouldn't be much of a difference...