S/O won't let me pay for anything?

My boyfriend moved here from Ohio a year ago. He is 19, living alone, making barely more than minimum wage, and absolutely refuses to let me pay for anything for him. I make decent money, I live with my parents, and I don't drive, so all of my money is literally just spent on stuff that I want. We went to get burritos a few weeks ago, and the total came out around $12, and as I went to pull out a $20 bill to cover it, he firmly stops me and pulls out the only $6 he has to his name to pay for it! He is wasting money because he feels like he has to be chivalrous! I've tried to discuss it with him and he won't have any of it. I can't get through to him. Has anyone else had this problem? Any advice? Thank you!