And that is why you are here!
It sounds like you got married when he wasn't working, is that right? And you supported your family for six months while he searched for work.
I imagine that was incredibly hard on you. It was probably also really hard on him -- most men are really demoralized, I think, by not being able to provide for their families. And six months of not having work would be lousy.
So now he's been working 6-8 months at a new job, and putting in a lot of hours. You probably thought some of the pressure would be off you when he started working, but in fact, you feel like you are now a single parent!
Are you sole custodians of his daughter, or does he have to pay child support to his ex-wife? Is it possible he owes back child support and has to get it paid off?
I don't think you are being unreasonable in feeling you need more support. I really don't. You are carrying the burden of raising two children, one of whom is not even yours, plus the debate about having children.
I think your wanting to have a child is reasonable and valid. But if he is working lots of hours to catch up financially, his head may just not be in the right place to make that decision clearly right now. Right now, he might say "NO" -- give him six more months in the same job, with some stability and the wolves away from the door, and his answer might be more positive.
Can you give yourself a holiday from making that decision for six months or so? I don't know if your age factors into it, but if it doesn't, why not take the pressure off both of you for just a little while longer?
If I've missed something, please write back and correct me -- wish you all the best!