Is semen a water-like fluid with no clumps in it, and does its color change? Is Wadi (pre-ejaculate) sometimes yellow? Do yellow, foul-smelling discharges after wiping nullify ablution (Wudu') only, or do they necessitate a ritual bath (Ghusl) like Mathy (prostatic fluid)? Does water remaining on the body after an obligatory or recommended ritual bath, which then runs down to the genital area and then to the legs, necessitate a ritual bath?

The cure for obsessive thoughts is to disregard them and pay them no attention. This discharge is not maniy (sperm/seminal fluid) because it issued from the urinary tract, whereas maniy exits from the reproductive tract. If you doubt whether the discharge is maniy or something else, you may choose and assign it the ruling you wish. Therefore, ghusl (ritual bath) is not obligatory for you unless you are absolutely certain that maniy, which necessitates ghusl, has been discharged from you. The water falling on the limbs during ghusl is pure, even if it touches the private parts.