mirena experience

I have had the mirena (IUD) inserted in me on Sep . 20.2012 and i was not on my period and it hurt like a *****. the first  month i couldn't stop bleeding and i had to wear a maxi pad all the time,though my period came on time and after i got my period ,it lasted more than usually.(2weeks)omg. The mirena is better than pill because i  believe u won't have to worry if u forgot to take your pill ,what worries me is that sometimes i feel after having sex that my mirena had shifted places,is that normal? and lately ive been having big cramps and lil blood ,which i hate,but im getting used too. Does anyone know what is small and red and looks like the size of a pill like round,cause i had this come out in my underwear and i didnt know what it was ,and i felt it was hard ,and i poke it with my finger and then lots of blood spalterd .like i have no idea what it is?anyone knows?please im like worrying. thanks.