Should i accept that it

I met my EX Girlfriend Savana in middle school and shortly after we started dating. We fell in love quickly and she was my first and really only serious girlfriend. She got pregnant at 16 during our sophomore year in high school. She gave birth to our beautiful daughter Merissa. We got engaged shortly after. I slept with her best friend and she broke up with me and broke off the engagement. I told her it meant nothing to me and i regret it. It affected my relationship with Merissa the most. It