When does hcg leave your system 😫

Had a MMC at 6w3d. I found out at my 7 week US. Had a d&c one week later. It’s about 4 days since then, and the test line is still darker than control line. My numbers were about 35,000 the last blood I got before baby stopped growing. Ugh. How long is this guna take? So frustrating.