I have been lucky that I only had one yeast infection in my entire life.  And that was due to medication.  It had nothing to do with my cleanliness or anything like that.  I had acquired a urinary tract infection, otherwise known as a UTI.  Well, the doctor gave me antibiotics to treat the urinary tract infection.  Little did I know that those antibiotics kill off the good bacteria.  Thus, the good bacteria in my private area was killed off.  I then developed a yeast infection.  Had I known that eating yogurt would live active bacteria cultures would give a yeast infection no more, I would have eaten tons of yogurt.