I do not know if any of this will work for you, but you can try several things.
* Use distress tolerance DBT skills when you feel like you are down and want to shop. * Postpone shopping. Tell yourself, "OK. I fell like I need to shop right now. And I will allow myself to shop, but only until after I..." finish the sentence with distractions like watch a movie or do the laundry or take a walk around the neighborhood. Or if you are feeling almost a desperate need to shop, then you could give yourself a time limit instead of a task. You would finish the sentence with, "wait 10 minutes." or "wait one hour."
*Try to sooth yourself in other ways. Maybe take a warm bath. Or read a favorite book. Or really notice and appreciate your child's smile. Or light a scented candle. Or pet your cat. Some physical sensation that pleases you.
*Remind yourself of times you have allowed yourself to go shopping and how that felt afterward. Ask yourself if you really want your behavior to make someone important feel bad? You are the someone important.
*Examine and break down your thoughts when you feel the impulse to shop. You know what you are feeling, but what are you thinking right before you have those thoughts? If you are thinking something like, :"Shopping will make me feel better." , once you recognize that thought, you can challenge it. If you no longer believe the fallacy that you are thinking (if, in fact, you are thinking this way) then perhaps the feelings will lessen too.

I do not know if any of these things will help, but they are all the things I can think of right now. I do not know if you are impulsive or not. If anything I suggest helps, then GREAT! If not, then just disregard it and move onto something else. I am not trying to assume anything about your shopping or your thinking or feelings. I hope I did not.

These are some techniques I have learned, mostly through DBT, but from some other sources too. I struggle with impulsiveness too. I struggle with intense feelings and have trouble tolerating them. Some of these techniques I use everyday, just to get through a day. Others I pull out occasionally, when things get overwhelming for me.

I hope that no matter where help comes from, that it come to you soon.