Must one repeat ablution and prayer if one feels something descend during them, then finds discharge after the prayer, knowing that it might be madhy due to sexual thoughts?

We advise you to stop these thoughts and ideas because they are from Satan. Increase your supplication (du'a) and seek refuge from him, and occupy your time with what is beneficial. If you are certain or it is highly probable that a fluid (sperm, pre-seminal fluid, prostatic fluid, vaginal discharge) has been discharged during ablution (wudu') or prayer (salat), then both are invalidated. Al-Nawawi said: "He does not leave until he hears a sound or finds a smell," meaning he knows of the presence of one of them. If you know that the fluid was discharged during ablution or prayer and you find it after their completion, then the ablution and prayer are invalidated. However, if you do not know of its discharge until after them, and it is possible that it exited after them, then neither the ablution nor the prayer is invalidated. In such a case, what is most likely discharged is pre-seminal fluid, which exits when thinking about things that incite desire. If these thoughts continue with an inability to stop them, and the discharge of pre-seminal fluid continues, then it is considered like سلس ( سلس البول - urinary incontinence or similar continuous discharge). If the discharged fluid meets the characteristics of menstruation, then it is menstruation, and a menstruating woman is not obliged to pray or fast. She must make up for the fasting but not the prayer.