IUD trouble

I got my mirena put in in September I think. I haven’t had any problems and my period has been non existent which is great. But for about 3 days I’ve randomly got heavy ass bleeding constantly and cramping which I though could just be a random period because the mirena does that. But now I feel very swollen inside and it feels like something is in there but I know for certain nothing is. Is this just part of having an iud ?