You've done really well for yourself buddy ~ congrats!!
These sort of transformations are a great inspiration for many people.
Unfortunately I think you may be stuck with the loose skin. There is no amount of exercise that can tighten loose skin. You are in a similar situation to a woman I know who had a bit of loose skin after childbirth. She resorted to cosmetic surgery to get rid of it after working her ass off in the gym trying to get rid of it.
You look better than the average joe anyway ~ I wouldn't let it bother you too much. If it bothers you too much, save up your pennies and get it cut off (maybe your parents could help???).
Looking great buddy!!!!