Really annoying

My fiancé eats so unhealthy and is the pickiest eater. He's never eaten a vegetable or fruit and is so hard headed, he won't even try one. We can't even go to a nice fancy dinner because there would probably be "nothing he can eat." It's probably the biggest turn off about him. I eat EVERYTHING. I told him I was worried about his health and it started an argument. He got defensive. I don't know what to do because I've never had to deal with this. We have a baby on the way and it already feels like i'm already taking care of one 😒