[shajo]

Hi all, I am new here, and I'm looking for advice.
My husband and his ex share custody of their two children ages 8 and 11. He has them one week and she has them the next and so on. During the summer months, I stay home as I work for the school system. So when my husband and I have the kids they are with us that whole week. On the weeks that his ex has the children, she brings them over in the morning and picks them up int he afternoon so I can babysit them for her while she works.
I feel like I'm being taken advantage of though because she has never offered to pay me, she shows up in the afternoon when she feels like it (no phone call she will be late), she does not even give us extra money for lunches or breakfast when they eat here in the morning even though they are coming from her house. We don't have a whole lot of money, we're not poor but money is tight. One day she didn't show at all, my husband called around 10 am and she had decided to take the day off and didn't even call.
I'm getting fed up, I asked my husband to say something to her and sometimes he does and some times he doesn't. I don't want my husband to think that I feel like his kids are a burden on me. Do you think I'm being taken advantage of? or Am I just being petty? What should I do?
Thanks for your advice