I have had a mirena iud for one year now and recently within the last three months I have random spotting every couple of weeks with a lot of stringy looking discharge that is brownish in colour. I am extremely active, I work out at least five times per week and play volleyball competitively. Sometimes it almost seems to aggravate my body after physical exertion. My OBGYN told me that the string was cut too short to coil around my cervix during insertion.