No gestational sac :(

Cynthia
So i went to the hospital tonight because I was a little crampy. They did blood work and urine sample and on paper it shows that I'm pregnant. But when they did the ultrasound they said that there was no gestational sac. My HCG levels were over 400. So the ER doctor said it could be an ectopic pregnancy or just too early to tell if there is a baby. Has anyone else experienced something like this? I'd like to know the outcome.