Am i getting taken advatage of?

I am 19, I am a single mother I live with my parents ( I have little help from them) and work full time and go to school in the afternoons. I work at a school where I am incharge of taking care of a severly hanicaped child. I enjoyed this job at the begining but now I feel like the school taking advatage of me. Because I am new. I used to have to work with her all day-7 hr day and then they brought in a gal to help me take care of her. So we switch of jobs. I take care of her for 4 hours and then she takes care of her for 2. This helped me out alot. We do various activities and we have to accomplish certain goal with this child. This student has bad hygenie issues! I feel that she is not being cared for very well at home. When i expressed my concerns, they said was that we could take care of it, by that they meant I could take care of it. I am extremely stressed, I was hired to teach her and do clean daily functions through out the day not to be a mother! I already have enough stress!