Thank Mother Nature for designing women with a yen for babies. It's built into our systems, from hormones to body to brain. It's historically necessary for the survival of the species, considering the demands of pregnancy and childbirth, the sacrifices required by an infant, and all the disease, famine, war, and other catastrophes humanity is subject to.
But unlike other creatures, humans have the ability to override natural impulses by using reason to make other choices. Just as we are able to override the natural limitations that keep other creatures under control. Human population is expanding at an staggering rate. Now that we are such a successful species that we are polluting the planet, crowding out other creatures, and even threatening the climate that all life has adapted to, it's time to value our ability to make rational choices. That shift in focus can make an enormous difference in how we feel. We can even end up feeling great about making the best possible choice for the good of all, which includes the babies we've already brought into the world.
It is possible to stop suffering over this, if your focus in on cultivating peace and happiness and investing yourself fully in the blessings you already have (I say this as a woman who adores infants, but stopped with one child of my own). Since your husband isn't subject to the hormonal longings you are feeling (and part of that is that you have given birth), he's already in rational mode. These are difficult times for the breadwinners and guardians of the family's well-being – the fathers. So you apparently have other good reasons not to have a child – like the long-term success of your family unit.
You might put your love of children to good use by getting a job working with children or babies. Even volunteer work. There are babies born with drug habits whose little lives you could improve by being available to hold and rock them, for example. There are children who need after-school care, or tutoring in reading. There are young mothers who would love to have an experienced, loving mom to help them with difficult babies.
I wish you the best. The feelings you have are somewhat like physical hunger. Just because we feel hungry doesn't mean we can eat everything we crave. What we want may be unavailable, it may be unhealthy, it may simply be too much. Think about how you calm your physical appetites to assuage suffering, and translate that approach to the baby hungries.