Should I ask for more money or quit?

I need advice!! I currently watch a relative’s two children with another on the way! I love them dearly, but I’m starting to feel like I’m being taken advantage of. I work about 30 hours a week, sometimes more. I clean the house, feed them, ECT. I receive $400 a month, and when you break it down, it’s less than $4 an hour. I’ve had to turn down job offers because the schedule conflicts with watching the kids. I intend to get an evening job, but they aren’t always home by 5, making things very difficult to do so. My question is, what would y’all do? Would you ask for more money or let them know you can no longer do it? Once the third baby gets here, the workload will double, and the pay is already not worth it. Help me lol.

I would most def ask for more money. Especially if you can get a better job!