Well, for one thing, stop imagining that he is starting this "wonderful life" with her! He's bringing all his own problems along with him and they are starting their marriage knowing they are both capable of infidelity. Nice start huh?
Second, acknowledge that you have had a lot of losses and stresses unrelated to him and that some of what you're feeling about his marriage is just transferring those losses onto his marriage.
Third - you'd be surprised at the healing power of being adored by a new guy. Honest.
(Haha - my ex was very bothered by my midlife moderate weight gain. But this weekend I acquired a suitor who thinks I look like a "piece of candy with legs" And my last boyfriend loved my ample booty - it was his favorite thing about me. Just saying, it's nice to be with a man who really appreciates who you are.)