Whether you are in the media, such as Elin Woods, or the unnamed spouse out of public view yet living with chronic deception, you may ask, "How did I get to this place?" Denial is one reason, not just your partner's denial but your denial. As partners of alcoholics frequently feel guilty for the behavior of the alcoholic - that if they were better partners, if they could just do the right thing, the alcoholic wouldn't drink so much - partners of those who are acting out sexually nearly always believe that his behavior is a statement about themselves. They believe they must not be pretty enough, sexy enough, smart enough, thin enough, alluring enough, ample-breasted enough, long-legged enough. The list is never ending.
You probably operate from the belief, "I need to do or be something different and that will make him stop." First and foremost you need to understand that you are not the cause of his acting out behavior. It isn't about you being different. He engages in his activity because of his own emotional wounding that now manifests in a pathological relationship with a mood altering behavior which for him is sex.
For years partners of addicts, irrespective of the addiction, have pretended that things are different than how they really are. When the addictive behavior is sex instead of alcohol or drugs, gambling, food, etc., denial for the partner is often accelerated because of the greater degree of shame and implied messages about the person acting out and the coupleship. Partners deny in an attempt to hang on to what is really an illusion, the fantasy that all is really okay. The fact is life is out of control; the addiction is in the driver's seat. But deny you must when you can't see your way out. It is a form of self protection.
After hearing time after time that you have quite an imagination, or that you are the one responsible for his unhappiness, or that it's your job to shut up and be grateful for what you have, or that you simply have trust issues, you learn to keep quiet. You keep fears and doubts to yourself while your self esteem erodes away.
Simply put, denial is dismissing your own intuition. It is blatantly overlooking what is right in front of you. Often there are clear indicators that you have a serious problem but you may choose not to see it. Denial stems from a yearning to believe that all will be fine or that all will return to how it was before this acting out behavior reared its ugly head. Do not chastise yourself for your denial but learn from it. It is a natural response to hurt and loss. Unfortunately it only perpetuates your situation and your pain in the long run. For your own well being it is critical you recognize the many ways you've rationalized. That is a start in stopping this well practiced defense.