IUD strings

Hi everyone,

So i have no issues with my IUD except for the strings. My boyfriend is a bit bigger then average and we love to go deeper when were having sex. Hes always complaining how the strings prick at him and now he has a little cut. I was told i could request for it to be cut a bit more but when i went they refused to cut it, because its got to soften out, but it feels like it almost got harder. And that it wraps around my cervix, but i think it comes out during sex

So my question is, what can I do to prevent it from pricking him? We tried a condom and that was ok I guess, just took away some pleasure.