So stretch marks mean i will have loose skin if i choose to lose weight? i'm 215 lbs, 18 years old and 5'7. how many pounds overweight am i as well?

Stop thinking and...: ...start losing. The average 67-inch 18-year-old woman weighs about 140 pounds. Estimate it by using 105 pounds for a 60-inch (5-foot) woman, and add 5 pounds for every extra inch in height (105+35=140). Take the next 2 years to lose 2 lbs per month, by eating LESS. Exercise is good too. Avoid sugar. Avoid simple carbs. No sugared drinks. Eat LESS. Two pounds a month for 2 years is 48 lbs of loss.