IUD questions and concerns!

Do you have an IUD? What are your feelings towards it? Do you feel it inside you? Does your significant other feel it? Could your SO grab the string when fingering?
For me, if he is exceptionally large, i can feel him hitting my cirvix and I'm afraid if I get an IUD, he'd be able to feel the string with his penis (or fingers) and maybe dislodge it? Please help! I'm nervous!