if you consider this an addiction then lets try and see how to heal from it. You enjoy crossdressing and looking at porn and it always ends up with you masturbating correct? It is not uncommon for crossdressers to do this. It's obvious that if you are masturbating then you are aroused right? If you are looking at porn then it makes you more aroused, so that explains why the porn element is there right? You want to become more aroused.
Obviously everyone masturbates to have an orgasm, but beside that what are you getting out of this behavior? What does this cycle of behavior provide for you? How do you feel after you've had an orgasm? What need does having an orgasm supply besides just the physical sensation of pleasure?
Perhaps the key to managing this behavior so that it is not running your life involves understanding what you get out of it?