Lost IUD strings?

So I have a copper coil UID and I can't find the strings at all. I've tried feeling around with no luck and I'm worried because I have frequent sex with no condoms (and my partner can't feel any strings either). I know I can go to my doctor but I was just wondering if any of you ladies could help me out with any advice on finding them, the worst case scenario, and if I should be worried/concerned. Thanks lovelies xo