So hurt and confused. I feel like my sister is using me,?

Seems like they are. Tell them that you're their sister and you love them, but you need them to work. Otherwise, what's gonna end up happening, is all of you will be kicked out of the house. (as in, by having to pay for everything, you wont have the money to pay the house payments.) If they refuse, start having them pay rent every month. They can't just mooch off of you. They'll get a job because they'll need to pay for themselves.