4WKS w/ cramping and consistent spotting

I’m 4wks today according to the app. I went to the er because my cramps changed and were more painful followed with spotting. At first it was dark brown then light red/pink and back to dark brown. It’s been an all day thing but not enough bleeding to fill a pad as I haven’t worn one. The er said my HCG is at 200, my uterus looks closed w/ no blood flow, but my ultrasound results said it was too early to indicate pregnancy. Has anyone experienced this? I’m so scared. It’s my first. I go back Sunday to get repeat labs at the request of the DR.