What should i do? 😕

So me and my S/O have been together 5 years about last year we decided to start TTC We Have a Great relationship & I couldn't ask for anything Better, but He told me the other night he's not ready to be a dad he's 21 and He doesn't wanna do it anymore! My feelings are shattered & I'm not mad at him in general but like I just don't understand I wanna explanation for it, Is it me or what ? I'm ready to start our family & I don't even know how to cope with it :( help