I'm 16 and haven't seen changes in my length or size of my p

Just because your penis hasn't grown much yet doesn't mean that it won't over the next couple of years. Is it 3 inches when erect? You are obviously going through puberty OK, as you have developed pubic hair. Have your testicles started enlarging? If not, I'm sure that this will happen also shortly. Please don't panic - and no, there isn't any need to try penis enlargement exercises - I don't believe that the actually work. I hope this helps. John