Opinions on having a baby?

My husband has mentiond on two occions of us having a child together-- we've been together almost 2 yrs, married three months- he's 45, I'm 32-- we each have one child from a previous relatonship (13 y/o girl, 9 y/o boy).. after his son was born, he had a vasectomy. A couple days ago, he mentioned (and I saw him internet searching) about sperm banks-- find a donor with his heritage; then he changed his mind... I can't take the see sawing. What do I say to him; should I do research, blah blah blah? I'd love to have another child, especially with someone I love so much, but he uses different excuses after a little while-- we too old, can't afford, etc... do I give up on the idea or where do I go?