Pregnant with IUD?

So I’ve had Lilleta IUD for almost exactly 1 year. Love it! No weight gain, no periods, no pain, nothin. But lately I’ve been having the exact symptoms I had when I first got pregnant with my son. Which I was in total denial about and brushed off pregnancy symptoms for over 2 weeks and called them flu symptoms.. but has anyone on here ever actually gotten pregnant while on an IUD? I know there is always a chance, teeny tiny, but still. I just want to know how anyone actually knew to take a test with the IUD. I check my strings every month and the last couple months, I’ve only been able to feel one string and it feels like the end of the plastic is sticking out of my cervix. Had a friend who said that was normal but I wouldn’t know.. I’m just so paranoid of getting pregnant again anytime soon and I think I’m just scaring myself into having “symptoms”.