We are not married but my BF is saying he wants a Baby?

He keeps rubbing my belly and saying how great it would be if we had a baby? He's 30 and wants kids I told him I want to be married before we have kid we been together for 4 years and are much in love but he wants the baby not marriage I don't get it? My best friend said thsts a red flag? But maybe he's just not the marrying kind? We said why get a peice of paper when we know our love? I don't know what to do??