if you're under 30 years old that's when Your **** is going to stop growing.
Well if you are serious, go to your doctor. There are alot of growth stimulators. But to be honest you might just have to wait on that till you are older. Your body still has alot of growing to do. Boys develop way slower then girls and although i am not sure on the growth rate of a penis you might just get a burst of size later. Plus it is not always length that matters, somtimes it is the circumfrence.