super short period

I have an IUD and normally my periods are pretty regular, about 24-25 days in between. This last time though, I was like 3 or 4 days late and when I finally got it, it was super light and only lasted for two days. Normally it's like medium flow I guess and lasts 5 or 6 days... Anyone else ever experience this? Should I be worried, or am I just being paranoid?