I don't think that what you are doing is very nice to your DH. He has adjusted to you not wanting more children. Springing it on him that you've changed your mind isn't fair. What happens if he doesn't want more children? What happens if he has started to plan a baby-free life and you start nagging about babies again? "Convincing", to most men, means "nagging until he gives in or walks out" - and many don't really want to walk out on their families.

I just know that my DH has changed his mind a few times (claims that he has never done that too) and the emotional turmoil I've been in from it. And it isn't fair. If you agree to something with your OH, you should stick to it. At least then people know where they stand, rather than living on the edge the whole time.
Totally disagree with this. People change their minds about things, and it often isn't based on logic, but rather emotion so isn't easily controlled. If you do change your mind about something as big as this you owe it to your partner to be honest about it. Who is to say your partner won't also have a change of mind. And if they don't, well at least you know where you both stand and aren't just pretending.

In my house, it takes two 'yes's and one 'no' to make an important decision like another child. I honestly thought the entire way through this last pregnancy and in the first 2 months of having bub that I would not have any more kids. Four was enough. I even contemplated getting my tubes tied. But I changed my mind.

I have changed my mind as often as I turn on the lights in the bedroom. DH know what I am thinking about things; but he also knows that it is a joint decision, and although I want another kid, and might try to convince him that another kids was a good idea, if he was completely serious and absolute in saying 'no', then I will go along with that. In our case, if he were firm in his decision to not have anymore, then he would go get the snip (I know, because we have talked about it) and I would support him, even if a little sadly; hell if he were that definite, I might even get my own tubes tied despite wanting another. But he isn't that absolute, because he knows I would like another at some point, and he knows that he may also change his mind (and very possibly I will change mine once again when he does). But it is a joint decision. You don't know how definite a 'no' is until you talk about it, give the person time to think about it, and then talk about it some more. What is marriage, if not compromise.