It sounds like you might have a yeast infection. Your dr should be able to determine this with a simple urine test. You'll need an antibiotic to get rid of it. Or check with your local pharamcist and see if they have something over the counter that will help treat it.
Treatment of vaginal discharge depends upon underlying cause. White discharge with rotten egg smell is due to trichomnal infection. Take 3 tablets/day of metronidazole derivatives like entamizole DS or flagyl for 5 days. If you are sexually active then advise your partner to take same medicine for same duration whether he has symptoms or not.