ZF
I had a mirena for 2 years and loved it but removed it as i knew i no longer want anymore kids so got something more permanent. Oh, plus the hot flushes i got about 1.5years into the Mirena was another factor.
My AF stopped completely about 6 months into the Mirena. No discharge at all. Just period free, which was absolutely awesome.
I would do a pregnancy test every 3-4 months to be sure to be sure, but all negative. I think what you have is normal. But if it bothers you, go get it checked out.
But enjoy being period free!