If you douche on a regular basis you need to stop doing so. When you clean out the vaginal canal you clean out all the good bacteria and provide an environment where the yeast (which is normal in vaginas) overgrows and develop into a yeast infection.
Also try to wear panties made of a breathable material such as cotton. Other fabrics hold in the heat- warm moist environments are ideal for yeast overgrowth.

If you already took medication and still you have yeast infection. You better visit a doctor so that he will be able to diagnosed and give you the right medication.