“I’ve been dating someone for two years”
Can I ask why you’ve engaged him in a 2 year relationship and never thought to mention to him you still want more kids?
“it’s not something I’ve ever mentioned to him because I didn’t feel like our relationship had gotten to that point yet”
I’m not sure why you have a line drawn for extending this reveal to somebody you’ve been seriously involved with. Newly dating is a whole other story but years down the road will be quite a surprise for him.
“he has mentioned a few times here and there that he doesn’t think he wants any more kids.”
Men usually know what they don’t want. He already has 2 kids and has formed an experienced opinion. You shouldn’t put pressure on him about this now that he wants to live with you. I assume he feels secure in the way things are going with you two and now that he’s ready to take up residence with you, you want to change his vision of you two as a couple.
“My question is, should I just go ahead and tell him about me wanting to have another baby”
Yes, but be prepared for him to remind you that he told you he didn’t want more kids and make a plan for how you’re going to handle that.
“so he can maybe just make the decision to break things off with me now”
You shouldn’t have manipulated the situation from the start. You should have been transparent with him from the beginning.
“instead of moving in together and finding out a few years down the road…”
Too late for that now. It’s already been years down the road.
“when the right timing would be…”
The right timing should have been earlier on in your relationship with him.
At this point, no matter when you choose to tell him, it’s going to appear as blurting it out.
Hopefully, he is willing at this point to be in all the way with you communication wise and handle the sudden news better than expected.