He's hot & cold about wanting a baby right now.

My husband has a two year old from a previous relationship. I've wanted a baby for about a year now. I have baby fever so bad. But he told me he wanted to wait a while, maybe a few years. Then I turned 22 and he said "I think 22 would be a good age for you to become a mommy." Then never said anything else and doesn't make conversation when I try to talk about it. Well, on Easter, we have 6 newborns in the family, and I was holding one, and he was smiling at me the whole time, and my husband said, "that makes me want to have a baby." He's said that a few other times, and he always gets my hopes up when he says it because he knows how bad I want to! Idk how to get him to talk to me about it and I can't tell when he's being serious because he's just hot & cold about it. He'll say things like that, but blow me off when I try to talk to him or figure out a timeframe of when to try for a baby. Help?!
Edit: I've been on birth control for 5 years. Sometimes he says "you need to come off it" then we have sex and he says "you took your birth control? Good." Ugh.