How do you talk to your boyfriend about wanting a baby when he doesn't cause he already has 2...?

Je
My boyfriend doesn't want kids any time soon because he already has two. We can't really afford kids right now either but still. I want to talk about it. Make a PLAN or something! We're planning kids in the future but it's just talk...
I feel like I can't talk to him about my feelings about wanting to have a baby because he's like DEAD SET on not wanting anymore... Idk how to bring up my feelings... And not being able to talk about it is causing me to deal with severe depression...
Do any advice on how to talk to my boyfriend about this?