Early ultrasound ?

hello! After 3 years of trying to get pregnant, I found out last week I am! went to my dr. the next day! my periods are irregular so it’s hard to pinpoint my last missed period. They did an

ultrasound, the tech didn’t see anything but pointed out a small little circle, told me to come back, which is today! 12/06/18, did an ultra sound saw a Yolk Sac but no fetus? again they said I’m too early to see anything and scheduled another one in 2 weeks. I’m worried though. Has anyone had the same issue ?

bottom ultrasound is my first one! I didn’t get a picture of the Yolk Sac ultrasound from today’s appointment