Arrggghh!! Why is this such a time chewing, exhausting decision??

I know I've seen this come up a lot so I'm not alone... how do you finally make that decision that you are truly done with having children... when there are lingering questions about if you might still want another?

I could go on for pages and pages about my pros and cons to having another baby but the short story is my heart wants one and my head doesn't. We have enough cons to having a baby to disregard the whole idea so I feel like I should just move on. And sometimes I'm excited by that idea. I love my two children and I'm so blessed I was able to have them and have such a great age gap. And now I could move on to other things that enrich our lives such getting my health and fitness and hobbies back into action and organising more travel and devoting my time to assisting both of them thrive (especially my eldest who has autism).

But then my heart wants a baby. That's all really. So I guess it's just my genes screaming "procreate" at me? It really saddens me to deny that though. I feel like I'll greatly regret it if I don't have another. Every time I look in the back seat I see an empty spot where my third baby is supposed to be. My longing is intense.

So tell me about your decision... I can't resolve this one and it's killing me and taking up too much mental space!