tired of waiting

how can I get my boyfriend to propose we've been together almost 4 years both 17 and have a 11 month old baby together we live together and honestly dont want to spend my life with anyone else he's in love with me just as much as I'm in love with him his reasoning for not wanting to propose is he can't afford an expensive ring and thats what I deserve he says I told him he could propose with a gumball machine ring and I wouldn't care