Weight gain/ weight loss after birth

Okay before I was pregnant I was 250 pounds I am now 27 weeks pregnant and weight about 255 pounds.. I’ve always been insecure about my weight.. my biggest worry is after I give birth and when I start to work out my skin will be very loose from the fat on my back, arm, legs, and stomach.. this worries me a lot because I use to be a smaller size way back but over the years gained weight fast and badly.. does anybody know any good workouts to not leave saggy skin after weight loss?