L.R.
I have a Mirena and my husband felt it, too. My doctor also said it's not too common. I had the strings trimmed. It helped a little. Mostly, I just had to wait a few months for the strings to soften. Now my strings are so far up and wound around me that he can't feel it anymore, but the doctor had trouble finding it when I went in for a check.
I'm thinking about getting mine removed. We want to try for our third in the spring. I don't know that I'll get another.