Sono er update

Today I went to the er cause I am prone to ovarian cyst .. I had bad bad left side pain , as per my app and lmp I am 6weeks 3 days they did an ultra sound at the er and there measuring 5 weeks 1 day has anyone else have this happen? They said everything looked fine there was a sac but no yolk or fetal pole.. am I just stressing for not reason! Thanks in advance

Update so I went for another ultra sound by my dr yesterday which if counting from the app I should be 8 weeks they told me I'm only measuring 6 weeks they seen everything and a heart beat has anyone else had this happened I'm freaking out and need some advice to keep me positive thank you