I totally, totally understand this and thank you for sharing your story.Your post is so incredibly honest and I will tell you, you are not alone in what you describe. When you say "fulfilling feeling", this is such an important thing.
I had a stage a while back, where I had been a full time carer for a family member who passed away. I began buying bits and pieces for my home (their room was bare, once all their things had gone) and it then carried on and on. Boxes would arrive and I'd feel elated, excited and happy from the purchase. The boxes would be stacked up, ready to open once I had decorated the room. Eventually................ the room was half filled with boxes there wasn't any room to decorate.
I realised I was simply attempting to fill a gap, a loneliness and to try and feel as you describe, more fulfilled. Once I had realised this, I understood that I wasn't really changing anything, I was purely filling my home with items that I almost certainly didn't actually need and while they sat gathering dust, fashions moved on and the items weren't that appealing anymore.
I also had a few months of buying clothing, also trying to feel better about myself (my uniform for almost 9 years had been joggers and t-shirts, because I never went anywhere due to caring). One of my family was having a cross moment one day and blurted out, I don't know why you bother, you never go anywhere - and again, I realised I was simply buying another item to fill that same gap.
It was helpful to find out what my "gap" was, in my case grieving and then to have some support. After that I began clearing away the unnecessary items and used the money from selling some of it (others I gifted away to charity) to clear the cards I had used to buy it all.
I've had one of my waffling on moments there but I thought I'd share as it might resonate with you a little
My “manic” buying started when I gave birth to my eldest, I suffered PND and definitely some sort of post traumatic stress from his birth so kept buying him clothes to kind of plaster over that void I suppose? It’s kind of like some weird fulfilling punishment I.e when you buy things and feel great but also are getting yourself into loads of debt. So crazy how the brain works. Anyway, I’m better now but still have this manic buying problem! Both my mum and Nan have similar traits though and I always joke I get it from them but hope to god I never end up in as much debt! X