Am I being petty and selfish?

So a month and a half a go one of my siblings needed child care of their kiddo. My sibling said "I will pay you with the child support I get" I said "Great I will need that money to pay for my midwife" (I'm very pregnant at this point and this is the only kind of work I can do at the moment) and my sibling said ok cool.

So I have watched this kiddo in addition to my own. In addition to over a week in overnights for my sibling to deal with things elsewhere. In addition I have catered to my siblings kiddos special diet (that has been braking the bank its not a cheap diet at all like its also nearly impossible to take this kiddo out to eat anywhere we go either so I feel like the kid is excluded from a lot too) I bend over backwards to make sure this kids included. Because I don't think its fair, you know?

Now finally the last part. Remember me saying the child support would be given to me in payment for providing food and care and such for my siblings kiddo?

For a month and a half including a week of over nights thrown in. And well over 150 dollars worth of food...I have only been paid 50 dollars. It was then my sibling told me I would be paid 50 dollars a week (I was paid wensdsy of last week) but if that was the case then I should have gotten 200 dollars for the whole month.

And now my sibling wants me to watch their kiddo for the whole weekend. And the weekend is when I get my break and my husband will be leaving the state on Monday for a whole week and I'm pregnant and I have 3 kids PLUS my siblings kid

I want to know if its petty and selfish of me for expecting to be paid for all the effort I put in to support my siblings child and to spend time with my husband and support my kids in his leaving for this coming week ?

I feel like a fucking horrible person since my sibling is going through so much and needs the help but I feel like I'm giving from an empty cup here. And my kids are gonna need me a hell of a lot this coming week. And I'm also mad I can't pay for my midwife...I just don't know what to do...

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