how often should a spc be changed?

My bladder was cut not nicked during a sugery and I have been told that the spc should be changed once a month. My spc was put in on July 18th and has not been changed and it is Sept 6th now. I have infection in my bladder and am now on antibiotics. Around the tube coming out of my belly greenish discharge comes out. I clean it daily with iodine (what my dr told me to do). He looked at it and said it was normal, I don't think so because I work in a hospital around infections all the time and it looks and smells like one to me. My Dr. cultured my urine but not the discharge. A wound care nurse told me it should be changed monthly (the spc) and that it was infected.