3rd time mom whp wants just one more...

My fiancee and I have a 4 yr old, 2 yr old, and a 5 week old and I want one more. Not right now but later and he's positive he is done. I am devastated I can't lie about that. I truly do want one more with the love of my life. I may change my mind as I get older I'm 23 right now and he us 24 but I can't lie I am upset. I don't want one right away but I do in the future. I don't know maybe I am over reacting to this situation