First IUD period?

Okay so this might be a vet odd question, but how long till you had like your first real period on the IUD? I have had days where I spot a little on and off since insertion about 2 months ago, the time for 2 periods came & went but today I've been bleeding mediumly heavy since I woke up. Horrible cramps & all the symptoms of a period so it is a period, but should I be worried it came 2 months late or is my body still adjusting? How long till my periods maybe go away???