ok when my second child was born I was absolutely sure I was done but declined tying my tubes because I've read of complications for some women. Still I was sure I was content with my two.
Well after my youngest turned about 6 months I started wanting another baby again, this never happened to me with my first (we waited 6 years to get pg again).
I told my husband and he said " Are you joking? we just had another". I thought he is right, I'm crazy. Now my youngest is 14 months and the longing has not gone away, I would never get pregnant on purpose but to tell you the truth I've thought about it because the desire is so overwhelming (I won't do it though, I don't have the guts LOL).
I mentioned it again about a month ago and he somewhat understood my desire, since he knows I'm serious about it, it's not just a what-a-cute-baby-maybe-I'd-like-another phase , it's like I'm sure I want another child to love raise and share life with so he is not so set agaisnt it now. he sees our two daughters playing and knows it would be a blessing.
he said that next year we can talk about it again, that's huge! that's almost a yes. my husband is pretty stubborn so him saying we'll talk about it is huge.
just talk to your husband, tell him you can do the diapers, if he doesn't like to do that. if it's financial find out ways to afford another, just have a plan ready and also tell him you want to have that experience again, he already has two of his own, you would like the same.
My sister married a divorced man who has a child already and he has a baby with my sister so was dead set agaisnt another since for him that's two. his oldest lives with the mother in another country so it's ridiculous that my niece won't have siblings just because he has responsabilities to his oldest.
anyways, I think you should go for it, but that's just my opinion. talk to him you might be surprised.
blessings!