I feel your pain. I too had the Mirena put in about a year and half ago. It took them about 2 years to figure out what was wrong with me. Though the Mirena has helped a lot with my pain it has not completely gone away. About twice a month I'm competely incompacitated with sharp stabbing pain in my right lower abodmen. I sought out a second opinion and the doctor isnt even sure if I have endometriosis now. I havnt experience any severe mood swings like you have though. In fact mine seem to have evened out. The doctor did say that it could take up to 3 years for the Mirena to work effectivly. I wasnt exactly pleased with that bit of information.
Somethings that I noticed that did help (especially with the mood swings) was exercise. I found myself in a better mood. I used the physicall activities to work out an frustrations and stress that was eating at me. I know that stress causes my symptoms to flair up really bad. I wouldn't suggest any excerise that works your lower abdomen muscles until your used to exercising (for me it only made it worse). But taking brisk walks and getting the blood flowing helped a lot.
I wish I had more to suggest, wish I had more that would help me too. I can tell you I'm tired of hurting all the time. The hard part is that people dont understand unless they have it.
Let me know if you find a break through :) and good luck!