I need advise

I help to babysit a family friend I work 3 days a week from 8.15 to 5pm sometimes 7 pm cos she pick me up and drops me.But then her house is super messy the she has like 8 kids every time I come to work I clean up but the kids are disorganized and messy too she said I should help her babysit her two youngest but is like an caring for the whole family coz in the morning there is this load of dishes I have to wash all their clothes everywhere I have to vacuum the house and most the mess are done by the kids I don’t babysit. And she pays $640 a month for all this and am 18 weeks pregnant . I don’t really know if she’s over working me and paying me less or is it normal because I have no ideal what to do as a Babysit and she pays me very late too. Pls I need serious advise.