Boyfriend Trouble

Ok so I've talked to my boyfriend multiple times about cumming on my back (I hate it) and he just keeps doing it. He did it again tonight and I tried to confront him but all he said was "well it's better than cumming inside you" and no matter what I said, he said that. Then he says "either let me do it that way or go buy condoms" but I can't even afford them at the moment because I'm between jobs. He has a job. I asked why he can't pay for them and he said "because you're the one with the problem". So I'm frustrated and I don't know how to resolve this... does anyone have any advice? No mean/rude comments please.