What do you do when your partner...?

Wow, Um, I don't think divorce is a good thing but if he cheated on you then I think that you are definetly not over reacting. Sending messages to your ex is just wrong. Okay, so like to catch up with a high school ex and just be like 'Oh, I havent talked to you forever! How are you?' but constant messages to an ex are just common sense 'No No's'. I would go to counceling, talk to him about it nicely, take him out on a date. Remind him of how he is effecting your children life. Divorce/Parental Separation can scar a child forever and even at a young age make them think its their fault so tell him that too if he wants to separate. If you still truly love him like you did when you first started dating, try your hardest to set his mind straight. After all, that's what love is. Good Luck. (You're not over reacting, anyone would think the same thing, just think it over first 'How will it help' with all your decisions.)