In my opinion, just grow up muscles isn't enough to grow strengh, and unfortunately most gyms focus on growing muscles because most of people go there for aesthetical purposes.
In order to grow stronger you must periodically be conditioning your muscles and focus on resistance and not on size.
Thanks for the tip! I've been doing that (doing pushups, seated row, shoulder press excersizes) I do both pushups on the hard mat, and also with one of those half-balance balls (I don't know the proper term, but I think that one builds core more)
I also asked a personal trainer to show me how to use the rowing machine properly (proper posture, etc) so I can get maximum benefit from that.
As for chin-ups and stuff.. I'm not at that level yet.. but I am trying to incorporate arm stuff in all my exercises (squats I do with a heavy dumbbell and every time I come up I raise it up, for example)
I'm really weak though.. I can do about 6 pushups properly, then I will either not be able to do any more, or my hips will start to sag down and that's not good.. so I rest and I try to do another 6.
And I know my basal metabolic rate (I eat about 1200-1300 calories a day) though according to that site, I should be eating:
"1133 CALORIES/DAY" to maintain my weight.. >_> I wish I could eat more..