IUD Post year confusion

Desi

So I've had my Skyla IUD for over a year now but my periods are all over the place. A few months ago I had it for 4weeks straight, this past week I've had 2 weeks of a period w/ only 4 days in between. Then there's always the occasional spotting for a few days. My OB says there's nothing wrong w/ the IUD itself (hasn't shifted), and all cervical/ureteral screenings are normal. Has anyone had a similar experience??