It is helpful to know that yeast can interfere with the sperm reaching the egg, but I do not think a yeast infection is a problem after ovulation.
I got the same exact distinction once when being tested for a yeast infection: negative results with a high white blood cell count. What I take it to mean now is that we didn't have enough yeast present at that moment to call it a positive test, since there should always be some yeast present in a healthy balanced vagina.
At the time I was very frustrated since I was still experiencing the symptoms and they were telling me nothing was wrong so they had no solution. The nurse practitioner at Kaiser was very dismissive actually and more or less told me to suck it up and use some vagisil. That was horrible advice because that product burned my skin and I threw away the bottle immediately!
Years later during a regular pap a very helpful nurse practitioner noticed that I had more yeast than I should (this is while I was not even experiencing symptoms.) Apparently yeast is very visible to the naked eye if you know what you are looking for. I now know that I suffer from candida overgrowth, and I have been using diet and probiotics to manage that for many years now.
Things to avoid when fighting off a yeast infection:
*wine (somehow this is the perfect storm for yeast! i had to give it up entirely

. ) other alcohol should be avoided for best results.
*sugar
*bleu or moldy cheese
*white flour (breads, pastas, cereals, etc.)
Eat tons of plain yogurt (I actually totally love it now and can't live without it - it is a quickly acquired taste.)
Drink plenty of water
I found the candida diet (google it) super helpful. Even if your infection is not chronic like mine it might help to get rid of the yeast quickly while TTC.