I feel depressed

Idk what to do im gonna be turning 21 in 3 months in May and been dating my bf for almost 4 years in August and i feel so depressed because i want a baby. Nobody understands why i want one so bad so i can never tall about it. I know i need tk be better prepared but i can't get it out of my head. And because i want it so bad i get depressed and will cry my heart out and my bf doesnt even know if he ever will want a baby in future but will tell me when he's ready if he ever is.... which isnt a lot of hope and it breaks my heart. I been wanting a baby for years but now my depression over it i feel like is getting worse and idk what to do.