Does semen that has gotten on clothes become ritually impure if it has mixed with prostatic fluid, knowing that semen is ritually pure and prostatic fluid is ritually impure, and that prostatic fluid does not appear on clothes by itself?

The cure for obsessive thoughts is to ignore them and not pay attention to them. Semen does not necessitate the emission of pre-seminal fluid (madhy) with it, and it is pure according to the preponderant opinion. It is not rendered impure merely by doubt about the emission of madhy, because the default is that it remains pure. However, if one is certain that madhy was emitted with the semen, then whatever it touched must be washed.