What about someone who prayed while ignorant of the nature of prostatic fluid (wady), and fears that his prayers are invalid?

We have previously explained what al-Wadi (prostatic fluid) is and what it entails. We emphasize an important principle: certainty is not removed by doubt. The default is that nothing has exited when in doubt, and you are not required to inspect. If you are afflicted with obsessive whispers (waswasah), you must disregard them and occupy yourself with acts of obedience. Know that doubt after completing an act of worship has no effect. We advise you not to repeat any act of worship that you are certain you performed, even if you later doubt its validity. However, if you are certain of its invalidity, then you must make it up.