Child support

I usually get child support for my two kids every two weeks about $100 or $120 each month but every month is not the same sometimes they dont put nothing but whatever they put I usually let it build up until I can save enough to buy the kids clothes or shoes well today the kids ack me for McDonalds and I am honestly broke so I payed with the child support card and omg the look the lady in the register gave me made me feel like I was doing something wrong for buying McDonald's with my kids money.. I didnt say anything but why would she even look at me like that ? I didnt understand

FYI I never took my kids father to court for child support he put himself in that situation to fight full custody for the kids but I ended getting full legal decision making custody.

Does anyone else who get child support and pay with the card ever get weird looks ?