I couldn't have replied to you any better than Danielle already did, Dutchmom.
And bear in mind that not only do the side effects suddenly jump up on you every now and then, but you may also be experiencing the 'normal' premenstrual stuff like the depression. I used to have that when I wasn't on Mirena, but not by far as long as when I was on Mirena, because I had the feelings I used to have before my period ALL THE TIME. Like one neverending PMS...