Feeling lost

So for the last couple months I've been working, and everytime I am trying to get ahead for myself so I can get a car my bf always gets mad. Like I've already given him n his family roughly 300 in cash in a month alone. Just to get things settled for 3 vehicles and whatever else for the house like new toilet. Well, he thinks I dont help out enough at all and I try and try to tell him what my plans are but he gets upset. He cant work but hes got 2 kids working plus me and whatever money he gets o the 3rd of every month is what they live off of. Every time I get my checks I pay my bill, and give 30$ cash for grocery like milk, soda, cereal. I tried keeping up with myself and taking care of me for once because I've never had the chance and I finally did but he got mad saying that I'm rich and I can go blow money like it's nothing all on myself but I've only spent maximum of 50$ on myself like new bra or something that has been needed for months. But I dont think he realizes that I've been giving up more money for them than I do for myself and when I go broke in the bank and no cash but maybe 5 cents in my wallet is what I've kept so far, he asks for me to give up money like I'm rich and he cant go to the bank and take out 20$. Hes kept maximum of 40 in his account.... but I'm not sure what to do anymore. I cant keep myself ahead anymore without him being g on my ass asking about my checks, what I keep in cash etc. I need a plan on how I can keep myself ahead.