Re: I can't take it anymore
You're not going to gain weight faster than 14 pounds in less than 6 weeks of training, whatever the program. Unless you eat more, and drink more milk.
Time for a reality check. That 14 pound gain is a more than 12% increase in your total bodyweight, in under 6 weeks. SS has brought your squat 66% higher than when you started ... and raised your bench by 35%.
In under 6 weeks.
Sure, you're seeing most of your bodyweight gains so far in your legs and hips - those are the biggest muscle groups. Sure, you're probably seeing a decrease in pullups ... your body's trying to adapt to the OTHER stresses you're putting on it. If you're unhappy with your progress on the primary lifts, STOP DOING ASSISTANCE EXERCISES LIKE CHINS anyhow. You're supposed to add them in only sparingly, and only when your progress on the primary lifts is helped by them ... not hindered.
To be honest, those gains are quite stellar. Another program won't give you faster progress, if your goal is increased bodyweight. The only way to speed things along is to improve your recovery.
So how much milk have you been drinking? The full gallon (4 liters) each and every day? How much food have you been eating? At least 3000 calories? How much sleep every night? If it's been 8 hours, increase it to 9, and take a nap in the middle of the day.
Patience! It's tough to be patient when you're a teen ... but project things forwards a bit. At your current rate of progress, by the end of August you'll have gained at least another 30 pounds, and quite possibly doubled your current squat performance. Maybe the same for all of the other lifts.
You truly think something else will give those strength and mass gains sooner? The only way to speed things, is to drink the milk, eat more, and sleep more.