Brown discharge

I've gotten the Mirena in mid March of this year and my period has just started to regulate and become normal and my cramps has subsided to being bearable when they're around. But this month, I've notice that a couple days before my period started, I was having dark brown discharge; not a lot. As my period began, the period blood was normal. And the dark brown discharge has increased quite a bit. I was assuming it's because of the IUD, and my uterus is still getting used to it but I'm not sure. Does anyone know anything about this, is it normal, or should I go to the health department (where I got the Mirena)?