Super anxious

I’m 5w3d today. Yesterday my HCG was 1827 and 3 days before 487. I know is increasing good but it is still pretty low and I’ve been taking progesterone suppositories since my first HCG a week ago that came at 47. My doctor ask me to go there tomorrow for a vaginal ultrasound. I’ve read that all your first Ultrasound are taking place upe to 7 to 10 weeks so I am really worried about why I have to take it so early. Could I be having an ectopic o an blighted ovum. This is my fist pregnancy and I’m terrified.