There isn't much of a set path for the growth of your organs. While most sexual traits develope between 12-18, it's very normal for the penis to continue to enlarge well into a man's mid-20s. As a teenager your scrotom should be tighter and will contract when you're erect. As long as that tightenning isn't painful or restricive of movement you're just fine. Your testes tend to ride a little higher and tighter when you're in your teens they are often not easy to feel in the scrotal sack as long as you're not experiencing pain in your genital region you shouldn't be too worried about where your balls are going.
If you feel your penis is too small that's probably the worst of your problems. Short of surgery there's not a lot that can be done but you could certainly talk to your doctor about it. It's possible you have health problems that are effecting your development but I wouldn't expect miraculess growth from any drug treatment or medicine. Instead I would suggest that you worry less about the size of your penis and just be happy that you have one. The penis is a miraculess organ at any size, every man's is different and there's nothing wrong with that.