Compulsive Self-deprivation

It's gotten to the point that I can't even let myself eat during meals or else I'm a fuck up.
I just wanted to go to the grocery and get shampoo. And to eat food. But I told myself not to give in to my hunger during dinner tonight and I did anyways. I messed up. I ate a lot of chips. Not even just a small amount that I could live with. No. A lot. And so then I couldn't go to the grocery because I'd already indulged in food. So I got to torture myself by watching them drive away. I was fine, until my mother came back and tried everything to get me to go with her and offered me a second chance. Of course I had to say no, as by now it would be a killing offense if I'd let myself indulge again. But then she left in a fit because I wouldn't let myself leave, and then I had to beat myself because I almost gave in to going to the grocery. And the worst part is I told her I wanted to go and she almost changed her plans for me, and I'm disgusting filth, no one should be doing anything for me.
I really want to tell the person I'm meeting up with tomorrow that I can't, just so my punishment really burns. But at the same time that would be quite rude to them. But it's not like I haven't lied before to them to punish myself. I'm far too spoiled. Which makes it difficult to end my pathetic, useless life because I feel indebted to everyone. Ugh.