We?re looking to determine if the person:
is continuing despite consequences,
has destroyed their relationships,
spends excessive amounts of time preoccupied with their behavior, and/or
has tried to stop the behavior and failed.
Sex addicts can even have psychological withdrawal symptoms from not being able to access the behavior. And they can build up tolerance as well. You can have people who are compulsively viewing pornography who have to use more and more to get the same effect.