BS here.
My WS went through the assessment process, so we know a lot about it. We were referred by our therapist to a psychologist for the assessment. We had an intake interview, then he did the testing, then we had a final appointment.
We were initially referred for bipolar disorder or borderline personality disorder. What we came out with was a laundry list but it really cleared a lot up for us. My husband was diagnosed with:
Mood disorder (not high enough for bipolar just yet but it is progressive)
Moderate PTSD due to time in combat
Personality disorder with 90% narcissistic traits and 90% obsessive compulsive traits.
The one area that my husband did not score high on for narcissism is that he has very poor self esteem, but all other area's he hit. Guess that's why he only hit 90%.
In any case, he gave us a plan of treatment to go over with our therapist and he's continued IC since.
Guess what though? That intake appointment? My husband was lying. We had a MASSIVE DDay 6 months after his assessment was complete. I mean EPIC DDay where he was fired for sexual harassment, 3 more AP's came out of the woodwork due to his lying. I won't even call it TT, it was outright lying. And I knew all along he had been lying, but I just didn't know what about and certainly had no idea to what degree.
Lying, regardless by omission, outright, whatever...kills. There is a saying that often it isn't the affair that ends the marriage, but the lies afterwards.
Your wife is giving you such a golden opportunity here. Your lying isn't about sparing her, it's completely about covering your own ass. Giving her the truth in little doses is eating away at her.
You CAN remember if you choose to. Sit down, start writing that timeline, don't put it off. Dig deep. Be the husband she deserves and stop hurting her with the lies. You made the choice to cheat on her, you make the choice to lie to her. If you can't remember something in the moment, don't say "there isn't any more" just say, can I have a day to think about this and give you the truth tomorrow?
Do NOT blame it on a "self" diagnosis off an internet search. First, there is a lot that goes into an assessment. Second, blaming NPD is an excuse. Just because my husband has narcissistic tendencies, it doesn't MAKE him lie. It's not the REASON he lied. He lied because he didn't want to get caught, period.