shapewear sizing is a NIGHTMARE

every single brand has different sizing and none of them make sense. i'm a medium in clothes but some shapewear brands say to size up, some say to size down for more compression, and some have their own weird sizing system that requires a PhD to decode. i ordered three different brands in what i thought was my size and all three fit completely differently. one was so tight i couldn't sit down, one was so loose it bunched up, and one was ok but gave me a weird muffin top at the waist. WHY can't there be a universal sizing system for shapewear. i'm going to lose my mind