How did you know?

I’m 22 years old, been married for 3 years and haven’t really sat down and thoroughly thought about being pregnant and having a baby. I have never fully let myself feel those emotions of what it would or could be like. I don’t know if it’s because my biological mother was absent after the age of 4 or what. I think I’m scared to be a mom because I’ve never had one. Idk. What if I’m not a good mom. How did you know when it was the right time to start TTC?