Glad to be of assistance!
What are you currently doing for your back work? I always found for me that I gained the most thickness from lots of deadlifting and barbell/dumbbell rowing, but was able to get things to "pop" more via better definition when I started to vary the planes I was doing back work in, since for years it was all horizontal rowing or deadlifting, no vertical pulling ala pull-ups or pulldowns, face pulls, etc. Then again, you didn't have a rear back shot, so there may be more to it that just hasn't been seen, but it looked like a little width could be a good thing. If you haven't done much heavy rowing (I mean, HEAVY, as in "feels like I could make 5-6 reps, but I'll do some breathing reps to get to 8-10) I'd certainly give it a try, and if you haven't done much for vertical pulling, try some weighted pull-ups whenever you get the chance. Sometimes just one small tweak of really pushing things heavy can make a LOT of difference, even if you may need 10 seconds between each of your final reps to be able to make them work!
Shoulders, that's one that just stumps me on size gains. I know I'd have great definition if I were single-digit bodyfat, but that's one body part that tends to not really show up well until you're incredibly lean, or, are gifted enough to have massive delts, which few tend to have without the use of anabolic substances. If you've been doing more isolation stuff for them, then try putting focus on some good stuff like standing overhead barbell/dumbbell presses, partial presses in the power rack, etc. and see what it can do. Like I always say, if what you've been doing hasn't yielded the results you want, then try something else and see what happens!
Legs, of course I always push the squat, but I did have big-ass legs just from leg pressing years ago before I started squatting (lifting plus skateboarding did well enough for me to get 'em big), but squatting took them to a whole new level. Sorry to hear the strain is still bothering you, I had a similar strain on the inside of where the groin meets the thigh for 2 months straight at the holidays, definitely no fun at all. Strangely, the thing that made it feel better was my return to leg work with deep hip belt squats and deep single-leg presses, not sure how it worked itself out, it just sort of happened. But, considering how many massive bodyuilders out there barely squat (or, squat light weight for lots of reps), it goes to show that you can still get plenty of size from other things, but of course, the squat will always be king in my book.
Just keep at it, you've got a great base to work with (and, for the record, it's better than that of most guys half your age!), and you've got plenty of time to keep getting better and better. Just keep working toward what you're after, check out a contest, and try new things and see where it takes you!