Pregnant with IUD?

Has anyone on here ever gotten pregnant with an IUD? I know it's allegedly supposed to be 99.9% effective, but there's always that one person that it happens to, right... So I have Kyleena and have had it since right after my 9 month old son was born. I don't get regular periods and can't remember the last time I bled any. The past two days I've been severely lightheaded to the point I left work early. There's no obvious reason I would be feeling that way. My mom asked if I could be pregnant and it's highly unlikely.. but I guess it could be. Have any of you experienced getting pregnant with an IUD? What kind of symptoms made you first suspect pregnancy?