as you told that you have undergone examination and investigations,
the possibilities could be,
1. physiological leukorrhea: it is white discharge which occurs physiologically before periods, at time of ovulation, during intercourse and in pregnancy
Many women mistake this to pathological leukorrhea.
If the white discharge having following features like,
no smell, color either like mucous or whitish, mild to moderate in quantity, not associated with other genital disorders it can be taken as physiological.
in case of this no need to worry as it is common in most of the women.
to inner ware: some women will be allergic to particular cloth material. In this case you change your panties better to use cotton material. Take bath twice a day and try to keep genital area dry.
3. improve your general condition as conditions like anemia
can lead to decreased immunity which will give assess to infection.
4. for white discharge both the partners to be treated if husband having infection the wife will get repeatedly.
consult your doctor and find out the cause for your white discharge and get treated accordingly.