Hi, I totally believe it could be the Mirena. I have had very similar symptoms and my doctors have come up empty handed. A few months back I suddenly got very dizzy and knew something just didn't feel right but just went to bed. I got up the next morning and every joint in my body was in so much pain I could barely walk. Was dizzy, and tingling and numbness in my hands and feet, I could go on and on. All the doctors have ever come up with is a elevated C Reactive protein test which indicates inflammation somewhere in the body. We have ruled out all of the scary diseases and my Neuro just shrugs his shoulders and says he has no idea.
To shorten this... I have asked over and over if it could be my Mirena and all of the docs say "not possible". I say BS because I had the Mirena put in in and a couple months later my body pretty much shut down. I finally had it removed last week and I am praying I get some relief. I am also looking at an autoimmune diet to see if it helps me at all.
Good luck, if you think it may be the Mirena I would suggest having it removed. We are the ones that truly know our bodies and if you feel it could be the problem you are probably right!