Fret not! I used to be like this (still can be messy, and am adhd I think).
The first thing is have less stuff
Put your clothes into 3 piles on the bed. You are aiming to get rid of 60-70 minimum. Makes piles of Stuff you wear, stuff you have worn in the last year, stuff you haven’t worn for a year. Put the last lot in a bag for Oxfam, put the first lot in the wardrobe. Go through the second lot again - anything you don’t like or doesn’t suit your lifestyle? Add it to the out pile. Then put the rest back in the wardrobe. You can revisit in 6 months.
Next rule is simplify how you store stuff.
Wardrobe - do you need more hangers? You need to be easily able to move stuff about. It shouldn’t be packed. (Chuck out further if it is, or put out of season stuff under the bed/order IKEA boxes.)
Draws - get dividers if they’re muddled up. Chuck out further if overstuffed. You are aiming to be able to just hurl items (jumpers, sports gear etc) into designated sections so they are easy to find and easy to put away.
Knickers and socks. I find it easier to have these in open baskets on top of the draws. One of the greatest decisions I made was to throw out my socks and replace with 2 designs. Never needed to pair a sock since.
Everyday Bras I have on a book inside the wardrobe so again easy to access.
Put Hooks on the back of your door, if you’re the sort of person who doesn’t like putting once worn clothes back in the wardrobe.
Get a couple of baskets to Chuck shoes in.
Books -
Aim is that all books go in bookshelf which is 85/90 pc full. Put them all on your bed. 3 piles - keep, maybe and chuck. Keep paring down till you can get them all on your shelf.
Put a bag/box by your door, and introduce a one in one out rule. Every time you get something new, something goes to oxfam.
If this is too hard, get a declutterer or a friend to help you.