It's posts like these that make me realize how lucky I am. I haven't been in a situation like this, and knowing my parents, I don't think I ever will, but I suggest talking to them about it. It might spark up a fight, but they should be confronted with the truth: you're an adult, and so are they.
You are family, but both still independent of each other, since you're both able to work.
As a side note, this kind of reminds me of Franz Kafka's Metamorphosis. I'm not saying you'll turn into a giant cockroach for letting this go on,
.
What I'm saying is it's not healthy, and it needs to change IMO. I know this can't and won't be easy, so best of luck.