Never ending MC

I started to miscarry on 10/18 at 4.5 weeks along. The scan and exam showed very little-no sack at all. I passed something last week that I'm guessing was my thickened uterine lining but I'm still spotting dark brown blood. This has been going on for 3+ weeks now. I had a miscarriage 2 years ago and ended up choosing to have a D&C because I was 9 weeks along and it was just too much to handle naturally. After the procedure I bled for about 3 days like a regular period and it was over. Why am I still spotting?! I just want to continue on and TTC our rainbow.