I have cheated on her 3 times, and at some points I completely forget about and show no empathy. Other times, I feel so fucking bad I wish I could never face her again due to all the pain I caused. She said when we first met I was the most passionate and caring person she’s ever met, but overtime she said noticed something wrong. I would get mad about random comments or actions and not talk to her for days. Then I would be completely infatuated with her, thinking that I could marry her. She was the most concerned because when we broke up I lied about the whole cheating incident, and she said my ability to lie was far to believable. I didn’t lie because I don’t care about her, I just didn’t  have the courage to tell her. She’s convinced BPD, but none of the traits became clear until now. I’m not narcissistic, I have just noticed I feelings about her that go up and down so drastically that I feel really lost. I don’t know what to think...