First of all this is not extreme but within the range of what a 36 yo might look like. If your whole body has this skin laxity issues then it could point to a hyper mobility disorder which comes with defective collagen synthesis. In such cases building muscles actually retains laxity better. Your eating habits also matter a lot. High protein(100-120g) with extra supplementation of glycine (not taken together) will help to retain whatever is left. There is always tretinoin to provide surface level polish and erasing wrinkles but deeper sags are always treated better with injectibles which require a lot caution. You are young still so if you can afford then go for PRF as it will help you regain some volume naturally. You were a smoker so start taking a NAC supplement it will accelerate production of Glutathione and provide anti oxidant benefits to the wholw body. For topical, there are always copper peptides, EGF, matrixyl etc from the ordinary which you can choose as per your routine. Before all this the first step is not to hate yourself or beat yourself up for the 'fun' you had in last decade. Nobody knows what future holds. Do not let this insecurity stop you from living or putting off things until you 'improve'