I agree with Fran. I totally respect your "desire" to adopt, although to be totally honest don't deeply understand it (only because it is a really heart wrenching process and its hard for me to understand someone "choosing" to go through...but with ALL respect).
I WOULD NOT force dh to adopt, this needs to be his decision. My dh, to be honest, also would not have done it had it not been for our infertility (and I probably wouldn't have either...but I digress). What dh said, to me, is not a red flag, but it's more his overall tone. People say "child of my own" but mean "biological" all the time without thinking, but some people (including my dh before he was really "into" the idea of adoption) truly DO feel like they want a child FROM THEM. THAT is a red flag, basically telling you he needs more time. Not that you can't talk to him while he is thinking about it.
Talk to him and explain things to him, but give him time to make the decision. But remember, you will also though have to be open to talking to him about getting pg as this is something HE wants too. The communication should be open both ways, and one of you will have to compromise. I think you should sit down and describe how you feel. See who it means to most.
For example - If you dont' want to go through labor because of stretch marks (which I'm sure that's not your reasoning, just giving an example
) then you may have to see that reason is not really valid if the reason he wants a baby is to have a genetic tie to him.
Hope this helps, Good luck!
Natalie