Hi Solo - glad to see you've bounced back from your little wobble. They do happen, but they will get less and less. I actually can't remember the last time I had one now and I've just celebrated a whole year of finding out my Tosser was still seeing his OW.
His was a mid-life crisis, coupled with an escapist world - while he was down in Devon with her once a week (he used to cover that area for business, she one of his clients) he could escape from the 'mundane' - menopausal wife, hormonal teenager, mortgage, normal home life - instead they were in this nice little "Mills & Boon" loved up bubble, so far removed from the real world I think he actually started to live the fantasy.
He even admitted to me one day that he'd told so many lies and stories to cover his ass that he lost the plot as to what was a lie and what wasn't.
His OW was the "love of his life, the reason why he was prepared to walk away from everyone and everything he loved to be with her, he'd never loved nor would again somone as much as her, blah blah blah".
Two weeks after he'd left me and she'd told him to bog off, this great paragon of his being was sadly forgotten and he'd moved on to his sister's best friend!!
He knew within about 3 months for real what he'd done, what he'd thrown away. But couldn't deal with it, knew I'd never take him back (did that in the previous Nov for 7 weeks before I caught him still cheating).
Their perception of reality is not the same as ours; I do believe that your DH knows exactly what he's done, but can't undo it so he has to get on with this new life he's made.
As for your new bedroom, would you believe it sounds very similar to mine! And I read in a magazine only last week that deep reds, purple and plum colours in a bedroom show a very sensuous side 
Keep smiling honey, keep saying it but you really are getting there 