I am 20 do I still have a chance after loosing weight to not have saggy skin?

I need to lose a lot of weight, for the past god knows how many years I have yo yo dieted, In my last weight diet I lost 4 stone then, due to moving and stress(I know, no excuse) put another 2 stone back on and to be healthy I now need too loose a good 90lbs/6 stone . I've been told because i'm young(im 20) there is still chance for me not have too much saggy skin if I lose the weight now rather than later. Is this true or will I have to end up getting surgery? Also any advice on good creams/exercises to help lessen the chance of saggy skin would be really helpful. Thanks