What Causes A Thick, White Sour Tasting Vaginal Discharge?

I am a 17 year old female and I have recently been experiencing a thick white sour tasting vaginal discharge with an unpleasant smell, my discharge used to be clear and slippery and it has been white and thick/creamy and sometimes clumpy for the past 3 months now. Ive been to the doctor and they confirmed that I dont have a yeast infection. I am wondering if this is normal and if theres anything I can do to stop this gross discharge as it has been effecting my sex life and self esteem alot, thank you.