Completely SHOCKED!

So I have the IUD, had it for over a year and we always use pull out method. He never cums in me. We are that careful.... Only thing is about two months ago I stopped checking for the stings on the IUD. My own fault. Well I have been sick lately and took a pregnancy test and came back positive. I did check my strings and it's still on there so I'm going to the dr today to suggest options if I should haven't removed or not.