Dr. Berardi's 7 Habits:
That's all the "dieting" you need for a while. Eat food, lift heavy things. Repeat indefinitely.
My line of thinking is: you're not watching what you eat and are probably eating alot of trash, yet you are still scrawny and lean. So why try to be restrictive when you eat? At 130 pounds, will it even matter if you get a little greasy, if you get more muscular? Ergo, eat a ton and pick a program to follow in the gym.
A gym membership would be good, or doesn't your school have a weight room you can use?