Why am I not getting ripped?

I am 15 years old, lifting the same weights 3 times a week with gradual increase in resistance to avoid plateaus, eating protein, and getting plenty of rest. Why are my muscles not growing? It's been 3 months now!

http://www.livestrong.com/article/223772-how-to-get-ripped-in-90-days/
http://www.livestrong.com/article/533442-how-to-get-ripped-in-three-months-at-the-gym/

You can look at these articles, and see what they recommend that you aren't doing. You can search tons more info on this site as well.