If you're still 14, I would recommend not worrying too much about how your weight matches up with your expected weight for your age or height.
Your body is still changing and developing, so more than anything else it's important to eat healthily, stay active and get plenty of sleep.
A combination of all 3 is the only way to remain fit and keep your weight at a level you're comfortable with.
How to tell if you are the right weight for your age
If you're really interested, there is a chart that shows you what your expected weight will be based on your height here:
(full chart here: http://www.cdc.gov/growthcharts/data/set1clinical/cj41l022.pdf)
But, as others have mentioned, you really shouldn't be too concerned about your weight unless you are on the extreme either side, which you are not.
The reason is that you will change a lot in the next couple of years, everyone goes through this.
But if you are not feeling confident with how you look, then there's no time like the present to do something about it.
A healthy diet (protein and vegetable based, cut out the starch, sugar and empty carbs) - and match that up with some light cardio every day (jogging and some muscle building) and you will have start toning up in a couple of months.