Found pictures of other women

This is what an addict does when they've admitted to being a PA and said they want help, but they don't really want to stop even though they've promised you they would. This is usually temporary, though. Since they're not technically looking at P (but instead, Psubs as @Kenzi pointed out), in their mind, they can tell themselves that 1) what they're doing is ok because at least they're not watching P anymore, and 2) they're keeping their promises to you and working their recovery. It's all just a bunch of rationalization crap, and typically it'll only work for so long before they're right back to P.

You said you found him on a chat site 2 years ago, and that's when he admitted he was a PA, but you haven't had any problems until recently when you found all the saved pics. What has he done in the last 2 years towards recovery? Simply admitting to PA does nothing except serve as the first of many steps which are necessary to begin recovering. If he hasn't done anything else between the incident 2 years ago and now, I'd say it's likely that his addictive behavior has continued since the first discovery. Maybe he hasn't done it as much or with the same sources as before (chat sites, etc), but a lot of social media includes material equal to P, IMO. The only reason he says he wants help now is because you found the stash. If you hadn't, he would continue feeding the addiction just as he has been.

It seems that maybe he hasn't really hit the point where he truly wants to recover. He is realizing that he has this issue, but that alone isn't enough. He also needs to recognize Psubs for what they are and understand that they are just as damaging to one's recovery. I'm sorry if this all seems harsh, but I want you to have realistic expectations as you go through this process. I'm sorry you're hurting. It sucks when the trust is gone.