can't stop obsessing about how he treats her

My ex narcissist and I were together for 9 years. He was divorced and I was a widow. We raised our children together. It seemed like the perfect relationship in every way. But he would create problems so he could run to other women. But when it didn't work out he always came running back. But now he has a woman over 20 years younger and treats her and her children way better. He has never opened his wallet for us, but happily buys them anything they want. So when I continuously read about how they will treat OW the same way...not sure thats true. He couldn't wait for his own children to grow up and complained about them all the time. Now he is ok with her 3 young children??? The only sense I can make out of that is he is finally in love and wants to make her happy. He started this a month after dating her. It makes trying to recover so painful for me. Why is she so much better than me?? Why is he willing to take on her 3 young children?