How much should you weigh if your 4 feet 11 inches and is 14 years old and has gone through puberty?

It depends on gender, body composition (whether you're muscular or not), and a lot of other things. But for a general idea, you can find you BMI (body mass index) by dividing your weight (lb) by your height (in), dividing that quotient by the height (in) again, and multiplying by 703.

so weight/height/height x 703

if you weigh 168 lbs and you're 68 inches tall, you would use

158 / 68 / 68 x 703 = 24.0, and that would be your body mass index.

According to a book I have, a healthy body mass index for 14 year old girls is 15.8-23.3, and for boys 15.9-22.6.

So if I did my algebra right, and you have an average body composition, somewhere between 78 - 115 lbs. But everyone is different, so that's just a very loose guideline.