Miscarriage and pregnancy levels ????

Hi ladies. So on August 24 I started bleeding and had a miscarriage. Probably about 4 weeks. The doctor wasn’t sure. So now it has been a totally of 31 days of bleeding and I’ve had 3 blood tests about 2 weeks apart to monitor my levels and make sure they were going down. Now the past 3 results were 22 mui. Then 4 days later it was 18 mui. And then a week later it is still at 18 mui and I’m having on and off bleeding still. My question is how long does the bleeding take and how long does it take my levels to go down because it seems they are just staggering and staying the same. Thanks.