Loose neck skin at 20, what are my options? (Photos)

I have always fluctuated in weight (90-125lbs) all throughout my late teens and early adulthood, never really smoked cigarettes (admit to regular herb smoking, though), and use sunscreen pretty faithfully. I know my history of bulimia adds insult to injury, but I am healthy and recovered now and am looking for the simplest solution to my neck issue. I have a small head so this looks weird! I know it isn't fat...