Well you might be angry and ask why shes better than you. And answer comes out simple - shes younger. Looks like he having more fun with that kid than you cause theres something new going on and guy enjoys having different kind of attention. Research shows that man prefers younger women cause they easier to live with. Less brains less trouble you know? He can manipulate her easy and she just blindly likes him for nothing. Maybe shes selflessly giving him her all without asking anything in return. Who knows. Difference is you been together for so long in mature relationship while they are in honeymoon stage and basically don't know each other, just enjoying emotions and early attraction.
You gave him chance. He decited to break up anyway. What else can you do. Move on. This will help you.
loveforum.net/threads/85672-Guide-How-to-deal-with-breakup
Doubt kills more dreams than failure ever will