Hi, I'm 19 And Have Had My Mirena IUD For

Hi, I'm 19 and have had my Mirena IUD for 2 1/2 years. The past couple months I would experience watery/whitish discharge for a couple days, every other week. and then soon afterward I would get the same discharge, followed by brown discharge with a lot of cramps and back pain. This cycle has happened monthly recently. I had bacterial vaginitis and chlamydia 7 months ago and got treated and cleared. At first I thought I had symptoms again, but the symptoms weren't very similar and I've had the same partner since then and we have been completely protected. Is what I'm experiencing more like a mentrual cycle or something that could have been caused by an infection and should get checked out?