Q. after urinating i always get doubt even when i have already washed it. Since i am working, it is very unconvenient . if i am home i can change my pant or use izar. Will my doubts nulify my prayer?

A. This doubt, unless it comes from a real condition of uncontrollable urine flow, is waswasa [excessive misgivings]. Take precaution against it by seeking refuge in Allah from shaytan the accursed upon entering khala', making tasmiya at the time of wudu' and tahmid upon exiting, and then the du`a: Allahumma ij`alni min `ibadika al-mutatahhirin [O Allah, put me among Your purified servants], and Allah knows best.