It is frustrating to go through all of this, especially when doctors don't want/know how to give clear cut answers. I'm 28 now and stumbled upon your story in doing research on IUD use with PCOS. I wanted to share with you that your experience of developing PCOS symptoms (weight gain, hair growth, all of it) mirrors mine exactly at the same ages, except that I was not using an IUD and I do not have diabetes (pre-pre-diabetic at most checks). I was actually taking birth control pills and still developing symptoms due to gaining weight (poor habits on my part). Given that PCOS seems to start to rear it's ugly head in that age range, and is very involved with the endocrine system, it is possible that you had PCOS which was unchecked with the Mirena as other forums I have read have noted that this happens to women with PCOS when switching from hormonal birth control to Mirena. Obviously every story is different but I wanted to share mine since ours seem similar. Hope you're finding some resolution.