Having more kids??

I am getting married after 5 years of living together. I have 2 kids (which are kind of his, because their dad passed away) and he has 1 that lives in another state that spends summers and holidays with us. I want to have one more and want to try ASAP, since i turn 28 this year want to have kids after 30 (i had mine very early on). He is still on the fence about it. I dont know what to do 😔😔