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

My girlfriend L and I were friends for a year before we started dating. I was with an ex M for 12 years (off and on) and, during my friendship with L, I gave M another chance. But with this chance, I found out that M had been cheating on me a lot in early stages of our relationship. She slept with her boss and a few others. She also was cheating on me during this chance. She slipped up on some lies and eventually admitted. 

L was a close, supportive friend during that time. I knew she had feelings for me. She told me when we first started our friendship. I was still hung up on M so I didn't share the feelings and told her. We chose to remain friends. After I broke up with M, my friendship with L developed more and after six months, we both expressed interest in more and I was ready. I love her.

We shared our past experiences to some degree, but I have a secret I will never tell anyone. It's something that I did 13 years ago. It was not against the law or harmful to anyone (except it plays on the mind often) and I don't know if it's wrong that I don't disclose the secret. It was something I did while I was with M. I won't tell Reddit either. It's too awful for me to write versus say aloud.

I am a responsible and caring boyfriend. We have a great sex life and we respect each other. We do chores together. We both have jobs. We are a team pretty much other than she is the boss of the kitchen (this is her insisting). I don't want to lose her. I love her.

Do you think it's okay to keep a secret? Even if it might change how your loved ones view you?
<bot>: I have a secret I've kept for 13 years. I have no interest in sharing it with anyone. Is it wrong to never disclose?