PLEASE HELP!!! 1 yr old Mirena & constant brown discharge

I’ve had the IUD (Mirena) for right at a year. Last period was 5 days late and much lighter than last time. My periods are like clock work. Two weeks after I started brown discharging (cramping in lower right side and lower back pain/cramping) everyday even up to today, and now I’m a day late again for my period. Not sure what my body is doing...had a ultrasound/pap/UTI test/Neg pregnancy etc and my dr said everything is in place and looks normal. So I have not a clue lol anyone else ever had this problem? Discharge is either when I wipe or in the toilet. Every now and then I start cramping when I’m about to discharge.