I'm on my second Mirena and can't believe that some people still choose the BC pill over an IUD
I also haven't had any children and during insertion experienced a sudden, sharp pain that faded very quickly. Afterwards I felt a little "hollow" and experienced light bleeding for a few days, but no pain. Everyone's experience is different; my friend landed up in hospital with a debilitating cervical infection and was forced to take heavy painkillers for weeks afterwards! (I think her doctor messed up the procedure...)
(If anyone here is looking for a more permanent method of BC that doesn't involve surgery, please look into the Essure. I highly recommend it and the process is no more envasive or painful than having an IUD inserted. I use an IUD in conjunction with the Essure to control bleeding. TMI?)