I Got An IUD (Mirena) Inserted In July. 2 Days

I got an IUD (Mirena) inserted in July. 2 days after insertion I started having symptoms of a UTI. It turned out to be Group B strep. Once on penicillin, I finally got rid of it. 2 months later I had another UTI. Again after a course of penicillin treatment it has subsided, but now I'm feeling the symptoms again. Most docs, including my gyne, says it's totally unrelated. I haven't had a UTI in 8 years and the only thing that was different was the IUD insertion. I have read online a bunch of other women who have complained of the same problem but usually it's e coli. Am I crazy or is there not a link between IUD and UTI? Thanks