having cramps and pms but no bleeding could I be pregnant on mirena?

I've had mirena  for about 4 years and have rarely had cramping or severe pms symptoms but I usually had a light period. For the past couple days I've been extremely moody and emotional, had heavy boobs, and mild cramping. Could I be pregnant or am I just experience irregularirty that comes with being on mirena? I sometimes skip a period but this time is different because of all the other symptoms. Thanks so much!