Sexual fantasies are thoughts that occur to most people, especially the youth, but they vary from one person to another with regard to their type, strength and effect. If a person imagines haram things that came to his mind unbidden, there is no blame or sin on him, rather he has to ward them off as much as he can.

Watching porn is haram in Islam; it is a disease, not a remedy. The one who does that is afflicted and he should seek to remedy himself by repenting and giving it up, not by making up excuses for himself.