general problems

First thing is, my period usually only lasts a few days[3-4], and i had sex about 7 weeks ago and now my period just lasted 8 days, off and on.It was also 2 1/2 weeks LATE! Lots of cramping and abdominal pain occured,heavy bleeding and lots of discharge[yellow and brown].I just recently had sex again today[2 days after my period just ended.]There was also A LOT of discharge again[it was really yellow & slimy] that during todays sex.idont know if this could be causes of Mirena or something else.Ive also never been checked to see if its in place in NINE MONTHS and i dont know how or anything! I NEED HELP!!