Probably relevant life and body positivity tip from a sewist, pattern drafter and seamstress:
The clothes are the problem. Please try to remember that you are not the wrong shape, size or dimensions. If the shirt doesn't button closed the shirt is too narrow, you're not too wide. If the dress sags at the back it's the dress pattern, not your ass. Absolutely nobody makes clothes that are Actually Your Size unless you custom order or make them yourself. Even then fitting is a skill and an art!

You're not the problem, the clothes are.

@sinituulia oh yes... and therefor I'm teaching myself to sew bras. or alter them. because "nah, we only have normal bras" when asking for something with more space between underwires or "you just can't wear a bra with wires" is just lame...

I did not have one single well fitting bra in my whole life. I'm 40.

@sibylle I make my own, these days! I do prefer them without underwires, but always put in upright short boning at the sides of the cups. It makes a world of difference in comfort and support for me, it's weird that's more of a vintage bra thing these days. I can't quite draft my own bra patterns yet so I'm happy about how many options to buy them there are!

@sinituulia oh yes, I bought two pairs of that kind recently. they were so comfy in the shop.
in real life gravity and weight made the wiring (boning?) fold in half (and stabbing my ribs) while also folding the cup into a weird shape as a side effect.

they just used some lightweight plastic strip as boning...

I work on a spandex sports bra design right now...

@sibylle I've used synthetic whalebone in mine, the same that gets used in historical costuming corsets. (It's a carefully engineered slightly more expensive plastic.) It's not right at the side of bust either, more directly under the armpit and to the side? I've not had it warp even in long line bras that need some four to five hooks to close. If you can easily source synthetic whalebone and switch to that, you might be able to use them again!