Nature has designed women (and many men) to crave more babies. That craving was once needed for the survival of the human race in spite of the difficulties and dangers of pregnancy/childbirth/childrearing, disease, famine, accidents and wars. However, we are now the most 'successful' species on Earth, to the extent that for decades we have been crowding out other life forms, and are consuming non-renewable resources, polluting and changing our environment at a rate that alarms those of us who study such things.
I had urgent population concerns when I came of age in the 60's. Since then, my concerns have only grown. I stopped with one child because this is so important to me. My parenting experience was full and rewarding; my child was happy and well-balanced and has turned out to be a wonderful adult and mother. She, in turn, has chosen to stop at one wonderful child, who is quite happy being an 'only' and will tell people who ask that he expects to father only one child when he grows up.
Siblings may or may not be happy with a new baby in the family. They may or may not feel jealous or deprived. They may or may not adore the new baby. The baby may or may not be happy, healthy, and free of special needs or medical problems. There are no guarantees, and you will see about as many positives as negatives when you look at other families who have gone for additional babies.
But if we realize that a great part of that baby hunger is simply our genetic and personal history at work, it might make it easier to make a clear-eyed choice. You and your husband will really have to work through your personal preferences, but in your "No, we have enough" column, I hope you will list the strain every new baby places on the survival system needed by all future children. This planet is smaller and more fragile than most of us realize.