Okay guys I’m confused...

I had a miscarriage around 8 weeks (the baby stopped growing around 6) I had a D & C December 5th. I’m barely bleeding - just a little brown blood here and there. We are ready to start trying as soon as I am done bleeding (my ob said we can start at anytime and there is no need to wait) Well for some reason I decided to take a pregnancy test to make sure everything is out and I still have a very strong line. Why would it still be showing up pregnant? What’s the point of a D & C?? I’m so discouraged. I just want to get past this....