I have a short torso! So where I bend at the waist is in immediate vicinity to thighs, stomach, boobs. It gets HELLA uncomfortable to sit in jeans, especially since my body shape requires high-waisted jeans. I have to unzip them in the car. Bad posture is a thing too but like, in the car doesn’t seem like a posture problem. I have been very slender and I have been curvy, and it always happens.
I think I’d like to partially blame the patriarchy too tho. We all know pants sizing is impossible and arbitrary and designed to make women feel fat. But also, Women’s jeans are all built with cheaper, thinner ingredients and a combination of no strength and a lot of stretch. It’s like, unless you buy something that’s gunna hug you, it won’t stay up. But men’s jeans literally are built stronger, thicker, and stiffer. I’ve tried them on and they are very comfortable! You could try shopping in the men’s section. But it can be hard depending on your ratio and body type, without modding them. Good luck!