When are you "fluent"?

I never know whether I can call myself fluent in Welsh because I can't express myself as easily in Welsh as i can in English. And I know that bilinguals/multilinguals often have different levels of fluency in each of their languages, or are more fluent in certain areas in one language but are less fluent in those same areas in the other language. But I always feel like such a fraud whenever I say that I'm "fairly fluent" in Welsh.
Something something not being a first language speaker of your country's minoritised language does things to your brain.