No. Way. 19 is way too young. And 20 is too young. And 21 is too young. And unless you are near 6 foot and 230 lbs at 7% bf with a full six pack (or 5'8" @ 210+ and 7%), you ain't even close your genetic peak yet. My bet is you aren't even close to that. Honestly I have never seen someone who had been training for the time you have been at your age, and had also reached their genetic limit. You have plenty of growth left. That's the truth, so please don't use genetics as an excuse for your young age.
Medical reasons aside (of course) there's no good reason to start using at your age. I will say that in my personal opinion the acceptable standard for beginning use does lower with advancing age...even as young as 24 or so... but you're not even old enough for your endocrine system to have finished developing. It doesn't finish until between 22-24 years old.You've got to live the rest of your life with that endocrine system! You need to take care of it.
The cycle however is simple, straight-forward and good. Save that for when you are old enough.