It’s not your own insecurities. He CHEATED ON YOU. This is not YOUR problem, do NOT flip this around on yourself. You are so young,  why are you willing to stay with someone who disrespected everything about you &amp; your relationship? Cheaters cheat because they do not respect boundaries, the relationship or cannot control their urges enough to be COMMITTED to someone! If you decided to stay with him without attending couples counseling to communicate better then there is no guarantee that he won’t just do it again. It wasn’t the girl who caused him to cheat on you, it was his own actions