IUD - Mirena Bleeding

I had the IUD inserted on May 21st. Spotted and cramped the first 2 days then completely stopped until AF came on June 6th. Had my AF, the day after AF stopped I had my appt. for the follow-up. Gyno poked around a bit and checked me and said everything looked good. Ever since then I have been bleeding/spotting at least once a day, sometimes more, and when I do it’s super dark blood clots. I had a miscarriage in April/May. Is this normal? I run daily and it mainly happens after I run and/or am being active, even as little as walking. Going on my 18th day of this.