What Causes Constant White Discharge From Vagina?

For almost 5 months now I have been having abnormal discharge. i went to the doctor and they tested me for STD's, I had blood taken, and i tried 4 different antibiotics over the course of the 5 months. All my tests came back normal but the discharge never goes away. The Doctor told me to just wait it out because the cause of it comming back could have been from the antibiotics. It has been about a month and i still have white thick creamy discharge everyday and during sex. Right before my last period I would have a light pink discharge but some days it would be just white. I have been off my period for 2 weeks and now the discharge is bright orangish red. WHY????