Skyla IUD inconsistent period

I have had my skyla IUD for 1.5 years. For the first year I didn't really get a period, just some sporting sometimes. Then the last five months I have been getting a light period consistently. This month I'm a few days late. Is this normal, or should I take a test? I know it's probably fine, I just have had bad cramps lately the past few months and hope nothing is wrong.