The Mirena IUD is placed in your uterus - you won't feel anything. There are 2 very small thin strings that attach to the end so the Dr. can pull it out when you want to have it removed. The strings hang into your vagina, but the Dr. will trim them very short. DH can't feel the strings when we have sex - he can't even feel them with his fingers. (they suggest doing this after placement to make sure it's still in)
You'll probably have period-like cramps for the first few days after placement but it's due more to the fact that they need to dialate your cervix to place. Since you've had a baby, it will be a hell of a lot easier (and less painful) for you to have your cervix dialated than for someone like me who hasn't had kids/been pregnant.
Estrogen in BCP causes migraines for me. The IUD does have a low level of hormones - but they stay pretty localized - not enough gets into the bloodstream to cause headaches for me. The other positive side effect is that most women see a reduction in bleeding during periods (and the lucky ones like me stop altogether.)
My insurance covered the IUD (or at least a portion) when i got it in, but doesn't cover it anymore. When I have kids, I'll have a new one put in, even if it means paying cash.
Re: Nico Leg : re Mirena IUD