broke and bummed

You know, usually I take pride in frugality. I don't have a big problem telling my kids 'no' when it comes to ice cream cones, excessive treats, toys (except for special events), and pricey outings.
Today hurt.
Today I mentioned to my mom that I was out of gas. I haven't had a child support payment since last July, so my cash has been limited to gifts and occasionally buying groceries for a friend with my food stamps and having them reimburse me. Mom wrote me a check for $30 in exchange for doing the laundry (yes, it does sound like I'm high schooler - thanks for noticing!) and I took the kids with me to the bank. While we waited for my cash, Catie started begging to go to Dollar Tree. I told her to calm down - she just kept going on about it. Finally I told her that I would give her a dollar for Dollar Tree if I had change after buying gas.
Before I sound heartless, I should mention that my Saturn Ion sometimes fills up for as little as $27. This time, however, my tank was very empty. The $30 was gone before I even had a chance to ask for a dollar to be held back. I could have asked that only $28 be put in, but I didn't. I put it all in.
Catie took it hard. She's still moaning about it five hours later. For some reason, telling my daughter that I can't afford a trip to Dollar Tree because we need gas cut me to the quick. There have been lots of time when I told my kids we weren't going to the dollar store because it was inconvienient, junky materials, etc. But admitting to them (and myself) that I can't afford a dollar store item stung.
We still go to the library - having the library email me two days before items are due has helped this chronic fine offender turn in her books on time. We go for bike rides on our super-thrifty bikes (that look really good). We bake cookies, bread, and any number of goodies. But that doesn't compare to a bag of Ring Pops apparently.
I try so hard. I make Catie dresses because long play dresses are hard to find in her size. I keep her home on a virtual school because socially and physically school was too much for her. Daniel is easy to care for, but I know the day will come when he turns on me to say that what I do is not good enough.
It would be different if there were money. I still wouldn't take them to Dollar Tree just because, but we would have that option. I would feel like a wise shopper, not a failure, if I walked past the Dollar Tree without buying something.
It's not easy.
I can't wait for this to change.