I'm I being taken advantage of?

Okay so I am a nanny to six kids. Ages 9,7,5,4,2,and 6 months. I only get paid $8/hr which is less than minimum wage were I live. I am also cpr and first aid certified, use my own car to drive the kids places/ run errands for the parents, etc. I feel like I should be getting paid at least $20 per hour. Both parents work full-time and can afford to pay me more, I just think that they are taking advantage of me. What do you think?