I had a missed miscarriage at 12 weeks in mid September and had it surgically removed on the 23rd of that month. I bled on and off for 3 weeks then had my first period 4 weeks after the surgery. It only lasts 3 days and was light, I then had a couple of days bleeding just before my supposed ovulation time, then a two day period at the normal time now I'm having bleeding again just before when I'm supposed to be ovulating.
I had a similar experience. Had mmc at 8 weeks (measured 4/5 weeks). Miscarried naturally but bled quite heavily for nearly 3 weeks. Bleeding never completely stopped. Had a period then went back to intermitent bleeding/spotting. Next period was really really heavy - just kept getting heavier and I ended up in A and E due to gushing blood. Turns our I still had RPOC - got given drugs to stop the bleeding and they sorted me out.
You need to mention this bleeding to your doctor. It could be just hormonal but it could be RPOC.