Tell him "I can't afford to keep buying all of this stuff for you. I like you and see a family with you too, but I can't afford to keep buying you all the stuff you ask me for. It's starting to feel like I'm a bank for you instead of a partner."

If he's serious about you, he should be receptive to how you feel here or have some sort of valid explanation as to why this happened. If he gets mad at you, think about this: why is he mad at you that you don't spend your own hard-earned money on him? Is this someone you really want to be with if this is how he looks at your money and opinions?