What Causes Burning And Itching In Vagina During Pregnancy?

hello. Im extremely worried right now. I am 32 weeks pregnant- Age 25, 5'5, and 180lbs and im having some itching and alot of burning... i checked myself and my clitoris is very red and swollen. Ive recently got tested for STD's and it was negative, so i dont think thats the problem. What do u think it can be? could it be from sweating alot? ive been moving all weekend...