Partner wants another kid already and I'm still in survival mode

My wife brought up having a second baby and I nearly spit out my coffee. Our daughter is literally 3 months old. I still feel traumatized from the birth experience, we're not sleeping, I have no idea if I'm doing anything right with this one, and she wants to jump right back in?

I love our kid more than I thought possible but I'm not even close to being ready to think about doing this again. How do I tell her that without sounding like a jerk? I don't want to shut down the conversation but I also don't think we need to make major family planning decisions while we're both running on fumes