Try to reverse this, R.. Pretend that, with two kids, you are DONE. You are done having your sleep interrupted, done with pregnancy and birthing, happy with how you've created your family and you are ready to stop.
Now, imagine your husband insisting that you get pregnant because it's really important to HIM. You would still be doing all of the extra parenting involved in having that extra child, but that wasn't a child you longed for, ached for.
You might grow to feel resentful of your husband and the new baby.
If you could avoid that stress and frustration, it's likely you would choose to do so.
I ask you to imagine those positions in reverse because I think you need to have some empathy for his position. Babies and children cost a lot of money and put a financial burden on the breadwinners in each household. Chances are, if you had a second child, opportunities to return to work would be difficult: child care for two children under 5 costs a heck of a lot, and that might be considered an 'optional' cost. Food, clothes, medical care and all of the other things which go with it cost a lot.
I have a sister who has three-- both she and her husband work. Her work pays for their private homeschool program and he works a good job with good pay-- and yet, they still have to save their money and really economize for the trips they take. They have to make hard choices. But the difference is that they BOTH wanted to have three children. With both parents on board, the financial burdens, the sacrifices of personal time and all of the parenting-- it's doable for them. They both feel they have *chosen* this.
My husband and I, however, are of a different mind. We were happy to have one, and then done. Personally, if he changed his mind and wanted more kids, I would likely feel rather resentful if he were trying to convince me to have more. It would be disrespectful of him to expect me to parent a child I did not want. You need to look beyond your own desires and stop thinking that there is some special, magic idea which will change his heart. It doesn't work that way. If he really wanted another kid, that has to come from HIM, not just to please you.