The solution, for me, are swatch books. I use little inexpensive photo albums. When I buy fabric, I cut a little swatch, staple it to an index card, write down how much I bought, and slide it into a sleeve. There may be several swatches per card, the writing obscured by the swatches. This serves multiple functions. I can compare fabrics for color, pattern and compatibility, with the fabric I'm considering; realize that I already have it; and know exactly what I have when I'm trying to match with something on the shelf; when I'm away from my stash, I can pull out the swatch book and start planning a stash buster from my little books. I wish I had started writing down where I got the fabric so I wouldn't have to go on a wild goose chase looking for more. Sometime there is information on the selvages, other times it's a total mystery.
Because I'm not a purse person, I shop with a back pack. The large compartment holds reusable shopping bags. One front pocket holds the swatch books, scissors, index cards, pen & pencil, mini stapler and staples and current coupons. The other pocket has the keyhole peeper, mirror set, red lens glasses, a bottle of water and a few granola bars.
When on a shop hop, I'll cut the swatches as soon as I get to the car and fix my cards so I don't repurchase something on the same day. Drives my girlfrin's loony as they refer to my OCD. So glad they tolerate me, we do have fun, sometimes at my expense, but fun just the same.