I've had this a few times.

I've found that when washing the girly bits, it is best to use water only. Sorbolene is also an acceptable alternative to soap. Any kind of normal soap, shampoo, bubble bath etc. can set it right off.

I have noticed that when I get thrush I am usually run down. It's an opportunistic little thing.

I've also tried wearing the yogurt internally and found that it worked for me. I put it in just before bed.