What Causes Fungal Infection Of The Vagina?

mrng i am having itching in the vaginal area.i went to gynic and she told me that i hav fungus ..sir may i know the reasons for forming fungus in uterus r vaginal area iam 40yers old,5.2" height,weight 55kgs and i dont have b/p sugar..my parents and husband also doent have the above..i have regular periods dont have any problem in my uterus..since from 2 months i am having this itching problem