Ultrasound

I have an ultrasound today to verify the pregnancy is in my uterus. Last weekend I went to the ER and they saw a gestational sac in my uterus measuring 4w5d. I got a call from my doctor on Friday, she seemed super anxious and said that since there were no fetal structures in the sac my pregnancy could still be in my tube and she wanted me to come in first thing this morning to check. I've managed to stay pretty confident it's not, but now I'm getting nervous as hell. I don't have an exact appointment time, so it's just going to be a lot of waiting around anxiously. I only have one tube, and last we knew it was blocked, so that's why there's some (a lot of) anxiety.