Ummm??

Desire

So just left the ER because I was having slight pains of course they reconfirmed I’m pregnant. So they do a vaginal ultrasound and tells me they don’t even see a gestational sac. Said It could be early. My last cycle was Dec 24.2018. What are the chances that it might be something wrong or is it really to early. Based off my last period I should be 4 weeks. I don’t know I’m just not understanding