I hate to piss on your parade, but you could have got the results you have, by just lifting hard and eating correctly. When I was 19, I was around 165 pounds, 5' 10". In one year I trained and ate my way to a solid 195... Naturally. I now weigh around 230 and I am a lot more solid (10 years later). I think you young guys are making a huge mistake by relying on roids for all your gains.
BTW, I would incorporate more bent over rows, and pull-ups in your back routine. If you are doing that already, fine, but if not.. do it. Cable pull downs will not build any thickness.
Other than that you look great, keep it up. Use your gains to pack on some real muscle now. You will probably lose some size, but your body knows that it can be that size and it will get there and surpass it.
Good Luck