Levonorgestrel
"I've had skyla in for about a year now, and it is by far my favorite form of birth control. Some background info, I'm 19 and have never had kids. Other birth controls affected my mood greatly, and Skyla has not affected my mood in the slightest. I also did not experience any weight gain. The only downside is my period is longer than it was before (10 days, but not heavy) and I experience cramping, but nothing midol can't fix. I can't even remember the pain from the insertion process now (which I got while not on my period), but that slight discomfort for a couple days it worth it for the next 3 years of birth control."