Quality cotton underwear/basics?!

I'm at the end of my rope y'all. 28yo woman.

Is there anywhere to find in this day and age relatively good quality cotton basic underwear in this country? I used to buy the h&m tank tops in bulk and probably underwear too but since a few years the quality of the new ones is thinner and worse than ones I've had of them for 7+ years!

I've tried Zeeman undershirts and underwear too but most of them literally unravel within a few washes which I've never had before.

I've resigned myself to sewing my own tank tops but I am specifically interested in underwear. I want full buttock coverage, I pretty much only wear black cotton and I prefer a higher waist (ie more hipster than slip). If someone knows of a good tank top I would like to know as well. Is there anyone who has recently come across something like this? TIA!