mama. I totally hear you. I just came through a long phase of this myself. Funny, the end of it coincided with my reignited desire to cook again! Some of the stuff I legitimately needed--diapers, a mei tai carrier, a couple of parenting books when I was losing my you-know-what with the kids and desperately needed an attitude adjustment--but lots of others I did not. Like, just how many homeschool materials does one actually need?
Have you considered that you're a little depressed? I know my problem was/is that I'm really ticked and sad that I'm still having to work when I want to be home with the kids, so I feel "entitled" to spend the extra money however I want. But that's not getting me home any faster! You've gotten some great advice already. I'm trying to replace the shopping with other small "luxuries" now--cooking nice dinners (not filet mignon, but I recently cooked Indian food for the the first time, it was a lot of fun), making myself generously sized iced coffees in the mornings with real cream and lots of sugar, having my DH take at least my older DD places without me sometimes so I can catch a break, etc.
Also, when I'm in phases like this, I like to surround myself with books on the subject and make sure I keep reading them, even if I only get halfway through each one. They help keep me on track. I've heard wonderful things about The Millionaire Next Door, and my DH also LOVES Rich Dad, Poor Dad, but I also recommend Affluenza. There's something about reading about the rampant commercialism and acquisitiveness in this country that offers a real reality check (not that I'm one to talk lately, but hey, we're talking self-therapy here
Mainly though, I think you should start being kinder to yourself in the ways that matter (the free or inexpensive ones), and maybe consider finding a good therapist if it's within your means (both financially and time-wise). I had to stop going to mine after a few months for scheduling reasons, but it was VERY nice to have someone who could listen to me without feeling guilty or defensive or angry on my "behalf" or like I was a bad wife/child/parent. It was extremely freeing and meant a lot to me.