Fertility after pregnancy

So I know right after pregnancy you are super fertile and I’ve also always heard breastfeeding makes getting pregnant harder. My question is at what point postpartum do you go from being extremely fertile to less likely? Is it just once your cervix is closed? I’m 10 wks postpartum, do not plan on going back on the pill (ever!!! I hate the pill 😡) plan on using primarily timing method. It took quite a while to get pregnant the 1st time and we do want more children, but I’m not looking for an Irish twin situation 😳( or anything close)