He's engaged to the OW

I heard through the grape vine that my ex-husband narc is now engaged to the OW. I didn't think it would hurt as bad as it did as our divorce was final less than a year and a half ago. Thoughts keep rolling through my head that he treats her better, etc. He bought her an engagement ring, never bought me one. Was I not worthy? Why is she worthy? These are the thoughts that are screaming through my head right now. I guess I thought I was over this and moving on. Is this normal? Why do I even care? Why am I even wasting any more precious energy on this a year and half after our divorce was final?