The talk about starting a family

Hello ladies and gentlemen! So how exactly do you go about talking to your partner about wanting to start trying? Should you wait until a certain time in your relationship? Last night, I pulled out a tub of ice cream and he jokingly asked if I was pregnant. However, he is uneasy about ejaculating inside of me during sex when I have made a notion that I wouldn't mind having his baby. I just turned 20 and he's 24. I don't want him to think I'm crazy for wanting to have "the baby talk" but I can't get it off of my mind and I don't know how to go about it.