If i lose weight will my skin sag?

please no rude comments.... ok i was 110 pounds three years ago and now im 170 im 18 years old and very depressed about my weight i have stretch marks its horrible.... im just wondering if i lose weight will i have saggy skin im not like huge huge. i use alot of lotion i heard that will make my skin elastic like and to lose weight slow. or if saggy skin could be hereditary my sister lost alot of weight and she had stretch marks and her skin isnt saggy at all... what im most worried about is my there 38c so will they sag?..... i just wanna know if anyone has tips. my goal weight is to be 125.