Being treated like a maid?

I'm 27 yrs old, have one child (4), recently divorced and have nothing to call my own. i have 2 younger siblings. one is 20yrs old and the other is 16yrs old and they are my half siblings from my stepdad. i have been living with my parents for the past 2 years after i left my husband. i was working but i got laid off and now i'm looking for work. i have no money for child care as it is expensive! i have tried government assistance (DSS) but because i am getting child support through them they take a percentage of it (for food stamps and F.I.) and i only get $473 a month and they like to give you the run around. i don't have time for that (i live in the south, so if you live in the south you know how DSS is down here!). so i stay home with my son during the day and trying to look for jobs, as both my parents still work therefore they can't watch him during the day and i don't know anyone that can watch him for me while i work during morning shift hours. anyway, while i'm at home i clean up so that my parents won't have to worry about that when they come home from work and it's only right anyway if i'm here all day. but just as summer started to come, my sister is home for her summer break and my little brother is in some kind of summer program at his school for an advanced program he's in. this is where the problem arises.....THEY DON'T MAKE THEM DO ANY HOUSE CHORES!!! it's absolutely wrong and unfair and they have to know it! i KNOW i sound like a whiny brat but, that's irrelevant to the situation. it doesn't matter how old someone is. when situations like this happen it can be irritating for anyone no matter how old you are! i wash dishes, clean the bathrooms, vacuum the living room and clean the room me, my sister and my son share. i have been holding my tongue for so long and it's really driving me nuts. whenever i try to talk to my mom about it she says she's gonna have them do some chores but does it ever happen? does she ever tell them to do it? NO. just last night, my mom was having a hussy fit about a dirt ring around the tub. for some ODD REASON, she always blames me for it. after i give my son a bath i always clean out the tub afterwards. then my dad and my brother got in the shower. did they clean it out afterwards? NO. but she has the audacity to yell at me for not cleaning someone Else's funk out of the tub! mind you people, we have 3 bathrooms and it's the only one that everyone uses because it's a full one. seriously, these are the reasons i feel like i'm being punished for these ridiculous circumstances that can be easily resolved. ONE: i didn't finish college like my sister is trying to do, i got married at 21, and now i'm back living with them. TWO: i don't have a job yet. it still isn't an excuse not to tell your other children to pick up after themselves or share the house hold chores and 2 just because i'm home during the day, doesn't mean that i have to be treated like a live in maid! i love my parents soooo much, but i really feel my stepdad has something to do with all of this. i have more to say but my question is long enough as it is. can someone PLEASE, help me to talk to my parents and try to explain to them how they are treating me so unfair???