My white blood cell count has been between 12.4 to 15.7 over the last five years and no one has addressed this problem what could cause this?

Have you asked?: My first question to you is "Have you asked your doctor?" and, if so, have you asked "Is this a problem"?" My best advice is to ask your doctor these questions. If your WBC count has remained stable for 5 years and you don't have any progressive symptoms, there's an excellent chance that the problem hasn't been addressed simply because there isn't a problem. That certainly is my hope for you!