Since you are young and may still grow a bit, you might luck out and have your skin fit nicely... it depends how badly stretched it was.
Anyway, Omega-3's are really good fats, generally thought of as fish oil. There are a few other places to get them, but not many.
There are some very good articles on this site dealing with nutrition, the different types of fats, and so on. Just spend some time getting comfortable with the search features and the article library.
In particular, read the beginner threads as they will link you to a lot of good information as well.
Finally, on a good note, you are fairly young, just keep learning and keep applying what you learn and over time you'll know a ton more and be in much better shape than most of those around you.