What Causes Spotting Inspite Of Having Birth Control Coil?

Hi I am a 47 year old woman and have had a coil for the last 5 years due to very heavy periods. Over the last five yearsI have had spotting during periods usually during ovulation time. However for the last six months the spotting has been nearly continuous but also seems to be worse when passing stools or after an orgasm either externally or Internally stimulated. I cant tell if the passing of stools is causing the bleeding or not. What do you think the matter is?