My husband did a lot of that sleeping on the couch thing when he was addicted to porn. He'd sleep on the couch, that way I wouldn't hear him get out of bed to get on the computer. He'd stay awake watching something on TV, then he'd fall asleep, and wake up around 4 a.m., and look at porn for about 4 hours, until I got up.
He only slept on the couch on his days off though. Once our computer was gone, he started coming to bed again. Until during his vacation, when he slept on the couch a couple of times, and then two weeks later, I found where he'd ordered pay per view.
You already found porn in his wallet.
Do you have the internet at home? check your cookies. Do you ever see the cable bill? Look for pay per view. Do you have seperate closets/bathrooms? Check the shelves in the closet, or under the bathroom sink.
If you find anything, you may have found your problem
If not, then it may be something else.