Positive a week after miscarriage

So, I just took this. I went to er a week ago due to bleeding. I had gotten several positive tests. They did a vaginal exam, and hcg was 17. My breasts have been very sore and I am still very tired and have bouts of nausea, hence taking a test. I also had an ultrasound that showed that I was in fact micarrying. The line was there right away. So hcg is going up and I'm still pregnant? Or could it be a weird hormone issue? Please help!