Levonorgestrel
"I had my Mirena inserted 2 months ago.  I am 23 and have never had children, and the insertion pain was not too bad, actually better than my normal cramps.  I'm still having very slight spotting, but no real periods since the insertion, which I'm very happy about because of my painful periods with likely endometriosis. I have a little cramping still, but not bad at all, and its usually only when there's pressure on my abdomen, like when I'm working out or need to have a bowel movement.  Also, I had to go on a non-estrogen form of contraception because I have migraines with auras, and I think these is a great alternative to oral contraceptive pills!  As a medical student, all the OB/GYNs I've worked with have talked about the benefits of Mirena."