abnormal uterine bleeding
"I am 22 and had the Mirena inserted last month. I had dysmennorhea that was so bad that for 5 days of my cycle I was bed bound on morphine tablets. My bleeding has always been normal flow and predictable. But painful with many trips to the hospital when my tablets were not effective. During the rest of my cycle I was functioning on codeine tablets. I had tried other methods to control the pain such as the pill which only made it worse and unpredictable. 
Since having the Mirena fitted, I have been off my painkillers entirely (only taken codeine for a couple of days over the actual period time). The fitting was only uncomfortable with no pain killers. I have spotted nearly every day since fitting but that is welcome in comparison."