Oh sweetheart, my heart goes out to you. It’s so painful to have a relationship end, especially when the other person goes back to an ex. While every situation is different, in general when a couple separates and one partner gets involved with someone new, it often highlights unresolved issues in the marriage. Him feeling obligated to try again, especially for the kids, is quite common.
The harsh truth is, you need to focus on healing yourself right now. Wondering if he made the right choice or if they’ll make it work will only keep you stuck in pain. Have faith that if it was truly meant to be with you, he wouldn’t have left. Lean on friends and family for support. Consider counseling to help process your grief. Most of all, be kind and patient with yourself as you put one foot in front of the other. Better days are ahead.