<human>: Summarize the given text in a few sentences.

Okay last night I went with my suspicions and went through my girlfriend's ( kim) phone. I know it was wrong. And I only checked the one app. Idk if I am glad that I was right or not. 

But essentially this was a fake number app which she used to pretend to be someone (kate) I had met off of another app. I met Kate via an anonymous post. And started talking there and eventually texting. I never once made plans to meet kate. However I did feel an attraction. I even showed the messages to kim. Both voluntarily and on request. 

This went on for 3 months if not a little more. And I continued to ask kim if she was kate. The signs were obvious. But I believed her. And I treated kate fine, but the conversations were sexual at points and at other times not. The other thing is that comparing the two girls, kate did things via texting that kim wouldn't do. Also no pictures were exchanged.

 But now last night, after one of the best days in our relationship. I found out that it was a lie. But before I revealed the truth. I asked kim once more, and she lied to my face with no hesitation. I called her bluff and we talked. Mostly me. And now I am at a loss.
<bot>: girlfriend pretended to be someone else and lied when confronted. Now feeling guilt for going through the phone but confusion because of the truth.