If a person suffers from severe OCD, does a dark orange spot that appeared on his underwear after washing the urethra remain ritually pure, even though he suffers from severe OCD?

What you did by disregarding the waswasah (whisperings of Shaytan) and building upon the fundamental principle, which is purity, is correct. You must do this every time the waswasah afflicts you until Allah grants you healing. So, whenever you doubt that something has exited from you, act upon the fundamental principle, which is that it has not exited. And whenever you doubt that something has become impure, act upon the fundamental principle, which is its purity.