I feel this so hard. I went for years - over a decade - not buying clothes simply because I COULDN'T FIND ANYTHING THAT FIT! Even if they carry my size (18-20), the clothes don't fit my curvy body. The waistband would have a huge gap in back, or the sleeves are too skinny for my arms, or the shirts are too short. And that's not even considering how most plus-sized clothes are just, well, ugly.
However, praise Goddess, I found Zulily and Torrid online. I've only had to return a couple of items, and they've been perfectly good about accepting them, no questions asked, and issuing me a refund immediately. Now I'm actually *enjoying* shopping for cute clothes that I actually like! It's still not as good as being able to go to brick and mortar stores and thrift shops, but at least I can find something to wear.