My (M27) GF (F28) cheated on me and I found out after 8 months of being lied to

I'm in shock, I don't even know where to start. I found out that my girlfriend cheated on me 8 months ago. <br>I'm a flight attendant and she is flying with the competitor so we don't fly together. We live together, we were in a relationship for 4 years. Never had any problems. I trusted her 100% as she trusted me. We had an open relationship regarding work: <br>we were allowed to hook up with passengers, fellow crew members, etc. It is very common in our line of work. <br>We always had the understanding that if it was a one night stand, we were ok with it. The only thing that we weren't allowed to do was to have a second hookup, that meant that the relationship wasn't only physical and that it went beyond that.<br>I never hooked up with anyone while working, not my cup of tea, but she did a few times and she always told me. I never had a problem with it, it's just sex, it didn't bother me.<br>3 weeks ago I had a very early flight (4 am) and while I was getting ready, she was asleep and her phone was on the bed. When she receives a text, the content of the message and the name of the sender shows on the locked screen. I saw the text, it said "did you get your period" and the name of the sender was a guy, let's call him D. I can't describe how I felt, I was so confused, I didn't know if I should wake her up or not. But I had to leave so I just put a note on the fridge and wrote "who is D". She called me around 8 am (I was already on the plane) and she told me that D is a pilot, they met on a connection flight, they had lunch together and she said that D asked her out a few time but she always said no. I wasn't very convinced about the story so I pressured her a little bit and she started crying over the phone. I was in a very bad position, I couldn't go back home, I was already on the plane and in a few hours I would have to start work.<br>She was crying and I was causing a scene so some passengers were starting to look at me so I believed her. When I landed I called her from the hotel room and we talked again. She was still crying and I just wanted her to stop crying so I told her that if D was just a friend I had no problem with it. She said that yeah, they were friends. And that was it. Everything went back to normal. I came back home and it was like nothing happened. We went to a party last weekend and she looked gorgeous, I complimented her and she had a big smile on her face.<br>On Monday she went to work and I stayed home. Around 3 pm I had the feeling that something wasn't right. I don't know how to describe it. It was just weird. So I started looking around the house. I opened her laptop and I found a conversation with D. It was from last week and it was just weird. It was something like "are you coming home this week end?" And she replied "no, I'll be home during the week" and he said "you have a boyfriend, right". I didn't think too much about it, I just thought that he was asking her out and she was declining and he was surprised that she was in a relationship. So I closed the laptop and that was it. The feeling that something wasn't right was even stronger. I started walking around the house and I opened her closet and I found a pair of jeans that she hadn't worn in years, it was the same pair, same style, color, etc. I didn't think too much about it. I closed the closet and that was it. Around 6 pm she texted me saying that she was going to delay a little bit because she found some former colleagues and they haven't seen each other in years. Cool. At 10 she was still at the airport. I texted her saying that she has been there for 4 hours and she replied saying that they haven't seen each other in years so yeah, they talk a lot. 3 hours later she texted me again saying that she had dinner at the terminal and she was heading to the car. At 3 am she was still in the car, I called her around 10 times but she didn't answer. I sent her so many texts, begging her to tell me the truth, that I would forgive her but please don't lie to me. She arrived around 4 am and she was like nothing, everything was fine. I was in shock. I didn't know what to say, to do, etc. I was crying, begging her to tell the truth but she was like "yeah, of course, we had dinner and then we took the car and I cried during the car ride because I'm PMS and that's it". It didn't make any sense. Who spends 9 1/2 hours with colleagues that you haven't seen in years and haven't talked to in years?? So I told her, please tell me the truth, I'm dying inside. So she broke down and told me. She said that she met D 8 months ago, they had sex on their first date, she said that D was better in bed than me and that she was addicted to him. They hooked up several times, always that she was working, and she said that she lied to me because she knew that I wouldn't be ok with it. I cried, screamed at her, begged her to stop and all she said was "sorry, I couldn't help it". I told her that I wanted to break up and she said "ok" so I left the house. I'm currently at a hotel, I don't know what to do. I still can't believe what is happening. I keep asking myself what did I do wrong and why I wasn't good enough. <br><br>UPDATE: I've been reading the comments for the last couple of hours and I want to thank those who have been supportive and kind. Unfortunately, it is over between us. Those who are saying that I can forgive her, I'm not sure. I'm not in a good place to make any decisions but what I do know is that I need some time alone. I need to get over the betrayal, the lies and all the mess that this has caused. I don't know how we can work this out. I don't know if I can ever trust her again. <br><br>I also want to address some comments: <br>1) I did humiliate her in front of the passengers when I was crying on the plane. I told her that and she said that she understood, she was crying too so I think it's ok. <br>2) She was hiding the texts and the emails, I didn't know that they were talking outside of work until I found the email that D sent her on valentines day this year. The subject was "are you my valentine" <br>3) Some people are saying that I'm the ah, I cheated first, etc. No, I didn't. I told her that we broke up before I hooked up with someone, I didn't lie, I wasn't addictive to the guy and I didn't say that the guy was better than her in bed. So...no. <br><br>So, thank you all for your support.