Hello honey,
what you describe is exactly what my sister & I suffered for years without answers. We both discovered we had systemic candidas which also linked to food intolerence. Our yeast infections returned every month as shortly before your period your immune system is less efficient, you probably crave sugar & a higher sugar in-take encourages yeast growth. The frequency of my sister's thrush was greater then mine but my pms symptoms were chronic every month. My sister's marraige was suffering & I could not maintain a relationship due to the severity of pms symptoms I suffered.
We both had to cut out, sugar, yeast, wheat & dairy from our diets. May I suggest you are tested for food intolerence, particularly intolerence to sugars & yeasts.
Since lowering my refined refined carb in-take I no longer suffer from pms. I have also persuaded reluctant friends with various pms symptoms to reduce their refined carb in-take & increase protein in-take from mid cycle. All were surprised that something so simple worked.
Cutting out sugar is not an easy task but I live by the mantra "feed my body & not my tastebuds"!
Hope you find this helpful & are reassured that there is a simple cure for
the constant yeast infection & pms.
Wishing you good health & renewed optimism