The fact of the matter is that everyone hits their personal plateaus. We all gain 30 to 50 lbs over time and reach a point natural stopping point. So ditto what Pure and others above wrote. It is all about putting more calories in your body than are being used. From your photo, it is obvious that at your age, your metabolism is still sky high so you have to eat, eat, eat. As you get bigger, your caloric needs increase. Train smart - don't overtrain body parts. Train heavy to force your muscles to respond. Do short as possible workouts - split routines are best. There are lots of exercises you can do for a body parts, so rotate them. And make sure you have rest days for your body parts. Don't pay attention to those articles or people that say you haven't accomplished anything if you haven't vomited after squats or you aren't staggering after the training or you can't get out of bed the next morning, Those are all signs of overtraining. Sorry to go on about that, but I get sooooo tired of watching guys in a chest training session, for example, do every exercise they can think of for that (or any) muscle group. Most are just redundant. It makes their muscles so tired it prevents them from growing. A tip here: make sure to get a high calorie drink (with some protein) after immediately after working out. Your muscles need simple sugars for glycogen replenishment.
P.S. don't waste your money on supplements. Most are junk, with little sound science and a lot of marketing money behind then with very few exceptions, such as protein (duh), I also stand by alpha lipoic acid, bcaas, creatine (use it in 6 week cycles, it stops working after that period), and if you want, natural testo boosters like tribulus (but you need to exceed the recommended doses). Stuff like nitric oxide is totally non-effective and drains your wallet more than anything.