A yeast infection causes itching or soreness in the vagina and sometimes causes pain or burning when you urinate or have sex. Some women also have a thick, clumpy, white discharge that has no odor and looks a little like cottage cheese.
These symptoms are more likely to occur during the week before your menstrual period.
Taking antibiotics sometimes causes this imbalance. The high estrogen levels caused by pregnancy or hormone therapy can also cause it. So can certain health problems, like diabetes or HIV infection.