I tell everyone on mamasoucre about my experience with Mirena. I had it in for about 6 months. For 5 months, i had constant bleeding ALL THE TIME! Around month 6 i was so relieved when it slowed down and almost completely stopped. One day i went to check for the string and it was gone! I panicked and called my obgyn. They assured me that it was just tucked up in there, but to make me feel better, made an appt. for 2 weeks later....
2 weeks later, after an ultrasound and a trip to the hospital for an x-ray, they told me it was gone!! Fell out!! That it was "probably in a toilet somewhere". In the mean time i was walking around unprotected for at least 2 weeks if not more. Come to find out i have PCOS and can't get pregnant anyway, but defiantly should have in the amount of time it wasn't in. I never felt it fall out, never saw it either.
I guess my case is rare, and the x-ray was to be sure it didn't end up in my abdomen, but all of these things are a possibility. I've heard almost all good things about Mirena. A lot of bleeding first, but everyone i have talked to says it's worth it and usually stops to no period at all. On the other hand, I've heard a lot of bad news for Paraguard. (lots of bleeding and horrible period cramps)
Hope you find the right choice for you. If you do chose to get one, getting it put in is not bad at all. Just a quick sharp cramp and a little bit of cramping after. Make sure you check for those strings though, all the time!!