SERIOUSLY!....When Should a Lady Ask Boyfriend if He's Serious about Marriage?

Please I need to know what fellow blog readers think about this - I have been dating this guy since March this year. He is nice, cool headed. We are both based in Lagos. I'm 31, he's 34.

Right now in my life, I'm tired of being called someone's longtime girlfriend. I'm looking for a man who is looking for a serious commitment. And when I say serious, I mean marriage and babies. So, at what point should I ask him if he wants the same without scaring him off? How do I even bring it up without sounding desperate, marriage or baby crazy?  

Would love to hear from TILB married couples too - when did the topic of marriage first come up in your relationship during your single days? Please help a sister out before I ruin this.