Are Irregular Periods, Fluttering Stomach And Fatigue Normal While On Mirena?

OI have a mirena had it since 2012 haven t had a period since than well in November 2014 I had a full period and one in December and one in January I haven t had another period since then I noticed a brown discharge when I go to the restroom and in the last week I feel fluttering in my stomach from time to time I m always sleepy What could be wrong?