I'm a teen and my nearsighted vision gets worse. will it keep getting worse? how can i keep it from getting worse?

Will stop in the 20s: As you grow through the teens, the power of eyeglasses if you need them will progressively increase although at a slower rate. For most this process stops in the mid 20s and stabilizes for many years until other issues of middle age sight start to happen. This is why most LASIK surgeons want you to wait until you are 23 or so prior to doing the surgery.

Nearsighted vision: First and foremost is the need for a thorough eye exam. You are so young to be developing problems with near vision that most experience as they age (presbyopia). Do not use illicit drugs - even occasional use of weed can cause visual problems. Make sure enough sleep and avoid any eye irritants. Other than those things, not much you can do unless a specific eye disease is identified.