Does semen (madhiy) necessitate a separate ablution (wudu') followed by a regular ablution for prayer, and what is your advice for overcoming the obsessive thoughts (waswas) of semen (madhiy) exiting during prayer?

The emission of madhy (pre-seminal fluid) nullifies ablution (wudu') and necessitates purifying the body and clothes wherever it has touched. A single ablution is sufficient for prayer after its emission. However, doubt about its emission does not necessitate anything. One must adhere to the original state, which is its non-emission, until certainty to the contrary is achieved.