I used the Mirena and loved it!! I used it twice (after 2 of my pregnancies) and was thrilled with the results each time and was able to get pregnant within 2 months of removing it.
I'm not sure if you LOVE your OB/Gyn or not, however, I don't like anyone telling me that something is ridiculous. I, personally enjoy having "friend-like" relationships with my phycisians so that if they were to ever say anything was ridiculous I would feel comfortable challenging them or telling the they were being ridiculous..in a funny way of course.
My two cents is remove it. If you have your own research that supports your symptoms then that is all you need. If the problems persist, at least you can eliminate the copper.
BTW: Mirena is plastic but does have hormones.
Good Luck..
:)