Hired a PI, found three girlfriends, cancelled everything

TIFU by hiring a private investigator to follow my own fiance and now our wedding is cancelled. My name is Rachel and I am thirty one years old. I was set to marry my fiance Derek in six weeks. Everything seemed perfect. He was charming, successful, and every friend I had told me how lucky I was. But something felt wrong for months. He started working late constantly. His phone had a new passcode. He would step outside to take calls that used to happen in front of me. My gut screamed at me but I ignored it because I loved him and did not want to be that paranoid girlfriend everyone warns you about. Then my best friend Monica saw him at a restaurant with a woman who was not me. She sent me a photo. My hands were shaking so badly I dropped my phone. I confronted Derek that night. He swore it was just a coworker celebrating a promotion. He looked me straight in the eyes and said I was insecure and needed therapy. I actually believed him for two more weeks. But the lie sat in my stomach like a stone. So I hired a private investigator named Frank. Best four hundred dollars I ever spent, or so I thought at the time. Frank called me five days later with a voice that sounded almost sorry for me. He said Derek was not just cheating with one woman. There were three. Three separate women he was seeing regularly, each thinking they were his only girlfriend. One of them even had a key to his apartment. My entire body went numb. I asked Frank to send proof because I could not accept this without seeing it myself. The photos arrived that evening. Derek kissing a blonde woman outside a hotel. Derek holding hands with a redhead at a movie theater. Derek laughing with a brunette in his car, the same car he drove me to dinner in every Friday night. I sat on my bathroom floor and cried until I had nothing left. Then something inside me shifted from heartbreak into pure strategy. I decided he was not simply going to get caught and apologize his way back into my life. I wanted him exposed completely. So I created a group chat. I found out the names of all three women through Frank and I messaged each of them individually first, gently, explaining what I discovered. They were horrified. Turns out none of them knew about each other or about me. We agreed to meet in person at the same restaurant where Monica first spotted him. All three of us sat waiting when Derek walked in for what he thought was a date with the blonde woman. His face when he saw all four of us sitting together, holding matching folders of evidence, was something I will remember forever. He tried to laugh it off, calling it a misunderstanding, but nobody was laughing. The redhead threw her water in his face. The brunette announced she was three months pregnant and asked if he even knew because he had missed doctor appointments claiming work trips. My mouth fell open. I had no idea about a baby. Suddenly this was not just a betrayal of me, it was a mess involving an actual child he had potentially been ignoring. I looked at him and asked one simple question. How many more women are there. He refused to answer, grabbed his jacket, and stormed out of the restaurant while the entire dining room stared. That night I called off the wedding completely. I canceled the venue, the caterer, and returned my ring through certified mail with no note attached. Two weeks later the pregnant woman contacted me again. She said Derek was denying the baby was his despite doing nothing to prove otherwise. She asked if I wanted to team up and expose him publicly through social media since he still had not admitted the full truth to his own family. I have all the private investigator evidence saved. of me wants to protect his family from public humiliation. Another part of me wants everyone in his life to know exactly who he really is before someone else falls for the same lies. Would exposing him publicly make me just as vindictive as him, or does he deserve every consequence coming his way.