While on mirena (levonorgestrel) and period stops all together, is it a gradual stop, or does it just randomly not come one month and no more period?

It varies: Mirena (levonorgestrel) can stop your menses, but that's not guaranteed. It can alter your menses (ie. Having light spotting in between). You won't know until after having it for 6 months. Most women i've known who get it, like it a lot and feel that the unpredictable transition period is worth it. See for more information: http://www.Mirena (levonorgestrel)-us.Com/after-placement/your-first-6-months.Jsp.