Is the discharge of fluid from the vagina, accompanied by sexual arousal, where it is difficult to distinguish between madhy (pre-seminal fluid) and normal discharge, considered a continuous incontinence that necessitates performing wudu' (ablution) for every prayer, especially with the difficulty in verifying the source of the discharge?

The cure for obsessive thoughts is to ignore them and not pay them any attention. When in doubt about whether something exited, or if it is madhiy (pre-seminal fluid) or vaginal discharge, the default is that it did not exit, or that it is not madhiy, until absolute certainty is attained. Some scholars hold the view of allowing a choice in the ruling. If discharge is continuously found upon wiping, its ruling is that of sals (incontinence), and vaginal discharge is considered pure according to the most authoritative opinion.