genuine question

i have 4 roommates. we all pay rent, utilities. but they want me to pitch in for groceries. i work but they just cut my hours. so i can really only afford rent, utilities and maybe gas. but heres the real kicker, my roommates get the groceries. they never return with anything i put on the list. mostly ingredients or fruit. and by the time i want some fruit its all gone. im rarely home for dinner. so technically im not eating anything they buy. with money i scrounge up i use for food i want and they all eat it without asking. and thats not the only problem im facing with them. i told them im not paying $25 almost every week for groceries and now i feel like im being exiled. i dont know what to do… HELP!