Sorry, I think your husband is right.
If he goes to college, he can get a better job after and make more money, and then you will be better able to give a child a good life.
You don't bring a human being into the world just because you want one.
You say you want a baby now. When the baby is a couple of years old and acting up and throwing tantrums, are you going to decide then that you don't want it?
The baby you have now is only three months old. You don't know what it's like to raise one child yet, and you want to have a second one already?