What is the ruling on praying if I'm unsure whether my wudu is still valid?

The governing principle is "certainty is not overridden by doubt" (al-yaqin la yazul bil-shakk): if you know for certain you performed wudu and are merely unsure whether something later broke it, you should assume your wudu is still valid and go ahead and pray. The reverse also applies — if you're certain your wudu broke and are only unsure whether you renewed it since, you should assume it's still broken and perform wudu again before praying.

This comes directly from a hadith in which the Prophet ﷺ was asked about a person who feels something during prayer and is unsure whether wind has actually passed — he instructed that person not to leave the prayer unless they are certain (hearing a sound or perceiving a smell), specifically because mere doubt, whispers, or vague suspicion (often from waswasa, obsessive doubt) should not be allowed to disrupt worship. In practice this means: don't let anxiety about "did my wudu break?" send you back to redo it every time without an actual, specific reason to think it did.

Source: hadith on doubt during prayer regarding passing wind, Sahih al-Bukhari and Sahih Muslim; general fiqh maxim al-yaqin la yazul bil-shakk.