GF's gyno said that I'm lying

So, my gf has a IUD and as some of you might have experienced before, it sometimes can hurt me when I go deep. It's not a terrible pain or anything like that, but still it's not nice to have that poking my dick when we fuck. We've talked about it before and she understands that it can bother me, so she decided to bring it up with her gyno to see if there's anything that can be done about it.

I was hoping that we'd be able to solve the issue but I couldn't be further from the truth. My gf told me that her gyno basically said that there's no way that it was true and that I'd have to be really big to even reach the strings of the IUD, but that she'd take a look and see what she could do. She didn't want to expose our intimacy to the gyno and say that I was in fact that big, so she didn't say anything to her. After examining her, the gyno said that there's nothing she could do, but it probably wasn't that big of a deal, since it wasn't likely that I was reaching it.

Anyways, does any of you have any advice on how to avoid getting poked?