Ultrasound at 6 weeks

Destiny • •Mommy of 2 boys {G.M.M-4/4/16 & O.W.M-1/16/18} 💙💛 •wife to H.M.M 💍 Expecting another miracle {May2019} 💙•Future teacher 🍎
I went in for an ultrasound and was supposed to be 6 weeks exactly. We couldn't see anything really though. All we seen was thegestational sac and the yolk sac inside of it. Is this normal? They didn't seem concerned, but I wasn't sure. I go back in about two weeks for another ultrasound.