Skims sizing

[changedusername190]

I dont post much but I need some shape wear and I’m can’t work out skims sizing. I need something strong as I need everything hitched up. My legs are ok but I’ve got a saggy tummy and large 34G norks that need industrial scaffolding.
Im thinking I need a mid thigh bodysuit but not sure how to work out the right size. Do I go by my bust waist or leg size..If it helps I can wear a normal bra.
Thanks to anyone who gets this far.

I'm a size 10/12 with 32 hh breasts and I wear a small but it is really tight and can only wear it for a couple of hours I have been known to remove it part through an event as it gets too much.