Take a deep breath. Sounds like an infection, not cancer. Why so quick to jump the gun and think that's what it is? It possible it could be something like BV (bacterial vaginosis) since also gives off a white discharge and any sort of infection is going to irritate the area and make it red.
Does the discharge have any sort of odor? Does it smell like fish or have a sour smell to it? Something else you can do is buy a Vagisil screening kit to test the pH of the vagina. Higher pH is also usually associated with bacterial issues and lower for yeast, though I would think your doctor would have tested your pH. She should have if she didn't. The doctor also should have taken the swab and looked at it under a microscope to say BV or Yeast, in addition to sending out the culture for growth. What exactly did your doctor do?
Any chance of an STD? I'd get screened for all that just to be safe. How old are you? Hormonal imbalances can show themselves as highly irregular periods, frequent periods, profuse discharge, etc. as well, so that's something to consider. When you say your periods are irregular and frequent what time frame are we looking at? How often is everything happening or not happening? Depending on your age and answers to the above questions, I may recommend seeing an obgyn that specializes in endocrinology, as they would be able to help you with issues about your cycle.