I think u shouldn't start exercise so early... u should ask your doctor when is the appropriate time to start exercise... better let your 子宮完全康復後才可以開始.. i also had C-section, i didn't start exercise after 4 months of giving birth... at the beginning, i just did some walking...
as u only gained 20 lbs., it is not that much ...after 1 month of giving birth, u will lose more lbs. as your water in body will be less... don't be rush la.. everything takes time!