I think you need to take an afternoon and try on some stuff. Do you have a Burlington coat factory near you? Or Marshall's or TJ Maxx? I won't pay more than $20 for any item, since i know we transition out of sizes quickly; those stores have decent prices. Right now I've been moving down a size after a month and a half. I feel like I'm getting a good number of wears out of things before I need a new size, and I'm buying only essentials.
I started in a 26 and had clothes on hand down to size 20. I'm now in an 18 pants and 16 tops. Old navy is good for me now since I can shop in the store. I've tried good will and thrift stores, was lucky to score a winter coat for $7, but other wise nothing. Plus sizes there are hard to find something decent without 20 hours of searching. And, oddly, I'm an 18 in Old navy jeans today, but the same 18's from old navy in a thrift store wouldn't fit. BTW, I hate their skinny fit!