Needing some help

Hi, I have been married for 5 years I recently found out my husband cheated on me. The women he cheated on me with knows about me. But he told her lies about me, I am a amazing women I have done so much for this man I know a lot of women say this I wish you all knew what I went through for this man. Well he didn't know AT&T backs up all your text messages all you have to do is back it up from AT&T account there was one night he came home drunk and it seemed weird because of what happened that night so I did what I did and snooped and found out that you can back up your old messages so I did and there was texting from him to another women talking about me and him saying how much she means to him what not long story short he is telling me he did it for sex he didnt mean what he said to her but he wants another chance he says he will take concealing anything to make it work idk what I'm going to do still but I do not is that I was to write that other women I want to know why, why she did it why would she do that why wouldn't she write or investigate more about me and his family his kids all of it what gave her the right to think it was OK I have so much to say to this person I don't know how to idk if I even should I just know that I want to it hurts me inside I'm so tore from this I feel like I need to write her like I should but idk how to or what to even say I need a women's help I need someone to talk I seriously have no one I am a stay home mom my life is my kids and dog and husband I don't have family his parents tell me to stay and work things out but they are not helpful I just really need help I'm so sick of crying I'm so sick of being hurt I need some help please