Is it ok to still be sad about an ex?

Ive never had a bf before my husband, yeah, had some heart broken and such. But still, they dont even bother me anymore. Thinking about it, im not even hurt bout it. Anyways, my husband was a divorced. Til this day, hes still really sad and upset about whatever happened to him and his ex wife. Whenever he talks about it, he gets angry and sad. Understand shes part of his history, but I just feel like this is so wrong, this means hes not over her yet? And havent let her go? I mean, dude, if youre happy with me, youll be happy it happened. Aint i right? Its been 7yrs since his divorce w his wife, but hes still not over it. When he talks about her, he doesnt even say "my ex wife." He said "my wife." Like who the fck am i to him?