As Ebon said, try
mass building exercises too. Try to keep your reps between 8-12, multiple sets, but high enough intensity so you're hitting MF by 8-10 and those last 2 are killers.
Thicken the wall, build the muscle, drop the bodyfat.
As for age, no one can attest better (in my opinion) to age being an irrelevent factor as well as Cursor can. (Check his pics out if you want some serious proof!!)
I realize that's not an issue for you (you stated you're 20), but I still wanted to toss that out there.
As for abilities, potential, etc., re: your age, hormonally speaking in terms of influence, you're fine, so that is not or should not be an issue with you.