Aita For Secretly Spying On My Boyfriend

AITA for secretly spying on my boyfriend after I found out he was cheating on me with my best friend? I never thought I would find myself in a situation like this. It all started a few weeks ago when I noticed my boyfriend, Mark, acting strangely. He was more secretive than usual, always hiding his phone and avoiding my questions. I brushed it off at first, thinking he was just stressed from work, but then I saw him receiving a text that made my stomach drop. It was from my best friend, Lisa. The message was flirty, and they had plans to meet up that night. My heart shattered. I could not believe it. My best friend and my boyfriend, together behind my back. I felt betrayed and humiliated. I wanted answers but also needed proof. So I decided to follow them that night. I parked my car a few blocks away and saw them meet outside a cafe. They hugged, laughed, and then went inside a hotel. My hands trembled as I watched them go in. I knew I should confront them, but I was too overwhelmed with anger and sadness. The next morning, I woke up with a plan. I snuck into Mark's apartment while he was at work and found his phone left on the table. I went through his messages and saw dozens of similar exchanges with Lisa. Flirty texts, plans to meet, and even pictures. I was devastated. I felt like my entire world was collapsing. But I also felt betrayed by Lisa, my best friend. She was supposed to be on my side. That night, I decided to confront them both. I invited Lisa over under the pretense of catching up. When she arrived, I told her I knew about everything. Her face turned pale. I showed her the messages. She broke down and admitted everything. She said she had fallen for Mark and thought he felt the same. I was furious and heartbroken. Then Mark arrived unexpectedly. I told him I knew about the affair and that I had the proof. He looked stunned, then angry. He tried to deny it at first but then admitted that he had been seeing Lisa for months. He said he was sorry and begged for forgiveness. I felt like I was in a nightmare. I could not believe I had trusted them. The biggest twist came when Lisa suddenly blurted out that she was pregnant. She said she did not know who the father was but she was certain it was one of the two of them. My mind spun. I had no idea what to believe anymore. I felt betrayed by everyone I cared about. I left the apartment in tears, unsure if I should tell Mark about the pregnancy or keep it to myself. Now I am wondering if I should confront Lisa about the baby or just cut contact entirely. Do I have any chance of saving myself from this mess? Or am I better off starting over completely? I need advice because I feel completely lost.