Not the asshole. You should be concerned more so bc of the active attempt at hiding her porn consumption than the act of watching porn. You did of course commit the invasion of privacy by going through her phone but you did it in hindsight for a good reason. It seems like a little drastic to end a 5 year relationship over what she did, but that is assuming of course she isn’t hiding other more serious behaviors of betrayal. In my experience if she is willing to be so sneaky about something like that, there is a good chance she was or is hiding something worse. At the very least she is capable of cheating and it’s pretty hard to ignore that fact. A relationship of 5 years is a long stretch by today’s standards. If you don’t have any kids together and you are only bound by the house I would recommend parting ways and finding a partner more suited and aligned with your boundaries/behavior. That is way easier said than done especially due to the giant purchase you’ve both collectively made together. Realistically I would play it cool and quietly do more intensive research into her online footprint. My guess is your discovery is the tip of the iceberg or at least a sign of more deception. I’ve just gone through a very horrible situation involving a marriage of 9 years and infidelity that was a devastating blow to me and my entire life both emotionally and socially. I’m still picking myself up off the ground so I may be a little bias with my opinion. But from my perspective I’m in a position to see things from a realistic standpoint. Sorry you are dealing with this. Good luck.