Hi M.,
I used Mirena for five years. I had it removed a few months before its due date. With Mirena, my periods disappeared altogether. I had spotting for the first few months and then nothing. This apparently is not unusual.
However, about two years in, I started to feel different. I was extremely fatigued and edgy. I couldn't seem to get anything done and boy was I crabby. I made an appointment with my family doctor who ran some tests. She suggested maybe I was depressed and prescribed an anti-deppresant. I disagreed because at that point everything in my life was fantastic and I could not figure out why I would be depressed. Anyhow, she was the doctor, not me so I took the pills. I was on them for a week and the feeling intensified, I felt like I was going to jump out of my skin. I stopped taking them and refused a different medication. To make a long story short (sorry) a few weeks later I had a period. After it was over I was my regular self again. I think that my body was just struggling to have that period and I had experienced hormonal surges.
Since I was back to normal, I considered this a fluke and kept the IUD. Looking back I was stupid to do this. Again I had no periods and a few weeks before I had the IUD removed I again started the same symptoms as before. This time they were more intense where before it was gradual.
My doctor assurred me that this could not be attributed to Mirena. That the hormone levels are so slight they could not cause my symptoms. I strongly disagree and in fact since it has been removed I again am feeling normal.
I have heard many positive experiences with Mirena, but I have also heard a few experiences like mine. If you choose it and feel "strange" I wouldn't waste time getting it removed.
As for me, I am back on the pill. Good luck, I hope whatever you choose works out for you.