You have a resistant strain
Resistant strains don't easily respond to diet and lifestyle changes. They're also a big problem because they will keep coming back even after you've been on the common yeast infection treatments.
This type of yeast needs a different approach. You need to get tested so that you can get a stronger type of treatment for it to completely go away.
You have underlying health problems
Certain illnesses can also make your body more susceptible to infections. A common one is uncontrolled diabetes which can create an environment where yeast infections develop easily.
This infection can also recur if you're on certain medications. Some medication can weaken your immunity, which then causes yeast infections to appear more easily.