Hi you can wear from day 3 itself.

I had c section

Do New Moms Need A Post Pregnancy Belt? Check this out . Also drink lots of water dont think about weight loss cz if are breastfeeding then u cant go on diet jst eat healthy dont eat oily . Breastfeeding helps in weight as well as fat loss. So cheer up !Go for walk if u had normal delivery do little exercise . Be happy