Need advice

Hey ladies I'm having a bit of a dilemma and need some opinions. Please no rude, mean, or judgemental comments. Ok so my SO is 48 and I'm going to be 25 in September and we have 1 child together. He has 6 other kids from previous relationships and doesn't want anymore kids, but I want one more. His response anytime that I try to talk to him about possibly one more child is always " I'm too old to be having any more kids! Isn't one enough for you?" is it selfish/unreasonable of me to want to have another child or is he not being fair to me? Idk sometimes when I try to talk to him about it it really hurts my feelings