Reoccurring yeast infection?!

Hey! I take cranberry pills daily, along with fenugreek. I have a reoccurring EXTREME va*inal itch/yeast infection every time I have sex with my partner. We’ve been together 4 years. I typically only have sex after he showers as his job is really hot and dirty. Even if he showers it still happens.

Is there something he can take/do to possibly help in the terms of my ph balance? I was thinking like a vitamin, but I don’t really know. He drinks a lot of vitamin water, never just WATER. He doesn’t eat much either so it’s hard to pinpoint the exact cause.

Thanks in advance!!!