why does this keep happening 😭

hello there

so not to be graphic or anything but over the last like year and a half I've been getting UTI's almost every other month. once it got so bad that it spread to my kidneys and I was in agonizing pain until they put me on antibiotics. anyways, after the first year of getting them so frequently I started making sure I was taking all the steps to prevent it. I make absolute sure I go pee after sex, I normally drink heavy amounts of water, I eat healthy, I exercise.. yet I still keep getting them. i get tested for STDs every 6 months and I was tested for that.. I'm not pregnant 1000% sure on that....now i have one again and the only thing I can think of that may have caused it is being dehydrated for a couple days . is it possible that I'm just prone to getting them ? no matter what step I take I seem to always get them