You may be suffering from vaginal infection. These infections come on their own as their appearance depends on immunity. Vagina has a peculiar structure. It is open at one en and it is close dta other by the attachment to the uterus. This vagina has a thick coat of layer inside which sheds cells everyday. These dead cells can act like a culture and allow many bacteria, fungi etc to settle there. There are cells in the vagina which secrete chemicals to maintain the vaginal pH to normal range. If the pH changes, the vagina becomes vulnerable to getting infected. The most common vaginal infection is fungal infection which can cause the white stuff which you have noticed. It also causes itching and foul smell.