I have sex once a week. I found out my gf has cheated before. Why can't I get over it?

I was talking to my gf earlier, 27F, and the topic of sex came up. She was just curious about my sexual history, how many girls I've had sex with, age, etc. I told her that I've only had sex with her (I'm 25M), and she got this weird look on her face.<br><br>She started telling me about her past relationships and how many guys she's had sex with. Most of them were in their 20s, but one of them was 45 and another was 32. Then she mentioned that she was in a relationship with this 45-year-old guy when she was 19, and they were together for about 5 years.<br><br>Later on, I asked her if she had ever been unfaithful. At first, she hesitated, but eventually she admitted to cheating on her ex. She explained that she was very young and stupid at the time, and she didn't realize the harm she was causing. She assured me that she has never been unfaithful to me and she won't be.<br><br>I've overcome a lot of internalized shame as a result of society's pressure on me to be a loser. Now I finally have a good girl who is faithful and has sex with me once a week. She is truly amazing, and I should just move on from this past and not let it affect me or our relationship.<br><br>&#x200B;<br><br>Edit: Oh my... How did this post get so many upvotes? Oh my... Edit 2: I won the bet with my friend lol. I didn't think this post would get this many upvotes.