I feel like the breakup is my fault

Hello. So basically our argument started because I visited her a few days ago and she was talking to a guy behind my back while we were in bed. She doesn’t even follow him on Instagram so it’s kinda suspicious to me. I asked her about it and she said he is just her old neighbor. She usually tells me if she’s talking to guys or not. I reached out to the guy for clarity and this annoyed her. A few days later she said she wanted to break up because of it. I wanted to fix things but she said I am insane and crazy and I need help. I got hurt by this and I said I feel like you don’t feel love for me because of what happened to your dad. She told me this on another occasion and I didn’t mean anything mean by it I was just trying to understand why she was being so mean. Her dad passed away when she was a kid and I totally get how it screwed her up. It wasn’t meant in a mean way. That is how she replied to that comment. Now she is saying if I didn’t say the mean stuff about her dad she would’ve been fine and we would’ve gotten back together despite telling me all day that she didn’t want to be together. I have anxiety and I see a therapist for it and her talking about my panic attacks and not understanding how breaking up impacts me really hurt. I feel horrible because all I had to do was not mention her dad and we would still be together. It’s eating away at me. Her responding to me by saying she is happy she cheated on me really hurts even if she was just saying it because she was mad at my comment about her dad. I feel horrible.

Reasons for my trust issues:

-She always resorted to breaking up - The tattoo incident - She is a flight attendant and a pilot wanted to stay the night. She said she will call me and ft all night to give me reassurance. She called me for ten minutes and hung up. -I talked about her communicating with me about guys she knew or was talking to. She understood how it bothered me but did it again a few days ago.