I am sorry to hear that you are dealing with this recurring problem. It really can get discouraging to go over the same territory over and over again, can't it? While I've never had this type of infection myself I do know that elevated blood sugar numbers can make you more susceptible to recurring infections.
Often a change in diet can make a difference in our body's response to infections. Has your doctor checked your A1C recently or done fasting glucose test? Do you eat a lot of carbs and sugars?