The media is an illusion. Those girls you see on TV weigh a whole lot less than what we see. Just stay yourself, and if you have concerns, just try a better "diet" meaning fruits and veggies, try organic foods, and less soda. Not diet soda, no soda...that will help a lot.
It does matter, not from a beauty point of view, but a health point of view. Generally someone in health care can help you determine the best weight for you based on your skeletal structure, body fat index, etc. Developing good dietary, exercise and health habits now, will serve you well in years to come. Don't rely on "charts" that tell you what you should weigh based on "small, medium or large" frame and your height. They are never right. In my case, my doctor determined my ideal weight to be 250#. Sounds like a lot, right? But it really isn't when you factor in that I'm 6ft7in tall. And the "charts" only list males up to 6ft2in tall. Lol.