Mirena long period and cramping

Okay so I've had the Mirena since the beginning of February and up until September I haven't been getting a period. Since then though I've been getting it regularly. The problem is that this time I've had pretty bad cramping throughout. Around day 5 or 6 it looked like my period was done but then today (day 7)  I've started up bleeding again, and even more than my usual period, I've also had bad cramps. I checked my strings but I'm not really sure if they're feeling longer than usual as they're not hanging straight down (kind of folded or curled up). So my question is, is this normal? Could my iud be expelling?