I caught my husband living a double life

AITA for going through my husbands phone and finding out our entire marriage was a lie. I need to get this off my chest because I am still shaking. My husband Derek and I have been married for six years. We met in college and everyone always said we were the perfect couple. Three weeks ago his phone buzzed while he was in the shower and I saw a notification from someone saved as Work Group Chat. I am not usually a snoop but something about the preview text made my stomach drop. It said miss you already can not wait for next weekend. I told myself it was nothing. Derek travels for work often and I trust him. At least I used to. That night I could not sleep. I kept thinking about that message so around three in the morning I quietly picked up his phone while he was asleep. His passcode was our anniversary date which honestly should have been my first clue that something felt staged. I opened the chat and my entire world tilted sideways. It was not a group chat at all. It was a woman named Priya. I scrolled up and found two years of messages. Two years. They talked every single day. They sent pictures. They had pet names for each other. She called him honeybear. I almost threw up right there in bed. But it got worse. I found messages about a trip to Cancun that Derek told me was a work conference. I found messages where he complained about me, said I was controlling and boring and that he felt trapped. I found a message where he said once the lease on our house is up I am leaving her. My hands were shaking so hard I almost dropped the phone. I did not confront him that night. I needed proof. I needed to see this through clearly without emotion clouding things. So for the next two weeks I became a detective in my own marriage. I set up a plan. I told Derek I was going to visit my sister for the weekend. Instead I booked a hotel one town over and asked my best friend Monica to help me watch our house. Sure enough Saturday afternoon a car pulled into our driveway. A woman got out. She had a key. She let herself into my house like she lived there. Monica recorded everything on her phone from across the street. I sat in that hotel room watching the video on a group call with my sister, crying and screaming at the same time. The woman spent four hours in my house. When Derek got home from his supposed golf trip he let her in and hugged her right there in my living room. I drove back that night. I did not call ahead. I did not warn him. I walked in and found them on my couch, my actual couch, drinking wine. The look on his face when he saw me was something I will remember for the rest of my life. Priya actually had the audacity to ask who I was. Derek said nothing. He just sat there frozen like a deer in headlights. I asked her the same question right back. Who are you to be sitting in my house. She looked at Derek confused and said you told me you were divorced. That was the twist I never saw coming. He had been lying to both of us. He told her we were already separated for a year. He told me nothing was wrong at all. Two completely different realities running at the same time for over two years. I started laughing, this horrible broken laugh because the absurdity of it all hit me at once. Priya grabbed her purse and left almost immediately once she realized the truth. She actually apologized to me on her way out which felt strange considering everything. Derek tried to explain himself, saying it was complicated and that he was going to tell me eventually. I packed a bag that same night and left for my sisters house. I have seen a lawyer since then and I am moving forward with divorce. of me still cannot believe six years led to this moment, sitting in a hotel room spying on my own home like a stranger. People keep asking why I did not just confront him the moment I found the messages. Honestly I needed to see it with my own eyes because words can be denied but actions cannot. So tell me, was I wrong for setting up surveillance on my own husband before confronting him, or did I do exactly what I needed to do to protect myself.