I had the tail bone pain, but it did go away after a few months. My left foot/ some of my leg is still slightly numb, even after over 2 years. It used to be much worse, though, so I count it as a minor irritation compared to some of my other Mirena trouble. For the insomnia I've tried some melatonin. It supposed to be a sleep hormone, and they even give it to children. (?) It seems to help with the loud music, static, and endless thoughts in my head so I can finally go to sleep. No effects in the morning so far.
I've read a lot of posts about how awful month 4-5 is, so hang in there!