I might understand your husband's feeling of not wanting to have another kid. For my case, I have a lovely 3 year old son, and i dont have the urge to procreate a new one because i have a potentially secured my bloodline and I just don't have that drive to make more babies. Although yes, I sometimes we do seek out sex, but its never about making babies its more for pleasuring our sexual needs.
My advice would be communicate with your husband, tell him how badly you want a baby, heck prepare a slideshow if you need to. We men will mostly give in to ideas if they have a solid reason that will benefit us.
If that still doesn't help, then work that emotion somewhere else. Give more love to your current child and nurture him to be a bright and brilliant kid.
Cheers,
Anon