IUD period returned after 2 years

I’ve had the Liletta for over two years, for the first year and a half I had like no period and now a couple of months ago it returned and I’m worried that it’s because the iud moved. I’ve never had cramps before my period but now I do and sometimes I feel nauseous during it. My period is also super light and brown and lasts only like 4 days (feels more like spotting). It’s been happening for a couple months and I saw my doctor about it and she said it’s fine and they could feel my strings but if it keeps happening to get an ultrasound. Has anyone had an experience like this? My strings were also cut a bit long and I can feel them really easily which makes me kind of nervous that i could’ve pushed the strings or something during sex