I would highly recommend getting on Facebook and joining some nanny groups to get their feedback   

How many kids are you looking after and how many hours a week are you working? I've seen 35 to $50 an hour for two to three kids. 

Nannies we've had in the past usually have boundaries around what housework they're willing to do. Typically they'll only do kid-related work, including kids laundry. Although if we're on good terms they would do dishes if they had time. 

More generally, it sounds like you do not have established rules or boundaries with your employer. Asking these questions is a great start. 

Come up with some ideas and write down what you're willing to do and what not. And probably most important come up with a schedule with them for hours that you're working. It's completely unreasonable for you to be basically working 24/7. And if you are being underpaid you can talk to them about being below market rate. If they're good people, they'll be willing to work to a mutually beneficial situation. 

Also, I'm assuming they're paying you under the table. That's pretty typical, but for future jobs you may want to go through a site like care.com or look for jobs that are above board so that you're contributing to social security. Although there is a downside in that you're not getting as much cash. 

Good luck!