G.♣.
If your OB said you don't have BV, she is saying that you don't have a bacterial infection. That's kind of the opposite of a yeast infection - not enough bacterial will help yeast grow. Yeast and bacteria keep each other in balance. If your OB said you don't have BV, I would think she also checked to make sure you didn't have too much yeast.
Taking probiotics and eating yogurt are ways to make sure you have enough bacteria in your system so that you don't have too much yeast. So it doesn't make sense that eating yogurt would cause yeast overgrowth.
I think you need to ask your OB more questions. And show her that rash. You are confusing bacteria and fungus (yeast). They are two different things that should be kept in balance. Not enough of one is going to cause too much of the other, thus causing an infection.
Talk to your doctor and ask questions until you understand.