Not trying but not preventing and he says no.

My fiancé and I have been together for three years now and we have always talked about having children and that if I got pregnant than that was that. Kind of if it happens it happens. I haven't been on bc for over three years now. And we barely use condoms and yet no baby. I've asked him when he would like to start a family and he says three to five years and I always thought I would at least be pregnant by the time I'm 20. I just turned 19 so you can imagine how anxious i am but when he said that my heart just sank. How do I turn off the snooze on his biological clock?