It may well be the right weight (body shape) for you, my brother is 6'4" and about 13, it looks right on him.
I used to be very overweight when I was about 18/19, so as a result I have a lot of leg muscle, and on me 14 1/2 looked awful, my ribs and spine etc properly showed, it wasn't nice.
It makes perfect sense to go more for health than image, you see so many guys in the gym that overwork certain muscle groups. I think this results in a freakish kind of image, I also tend to do mainly cardio.
you seem like have a body that is hard to put on weight.But u can put on some weight and toned muscles by combining your work out and diet habits.you must have a large amount of calories 500 or more.Also you can try some white meat chicken and fish.And have some fresh fruit and vegetable juice with nothing added artificial.
The single most important thing you can learn to do is squat and deadlift with good form. Reps of 3-5 and as heavy as you can go whilst maintaining good form. Do this twice a week (squat one day deadlift the other) then on the other gym day do your bench press, chin ups etc.
Stressing the whole system under significant load (safely) will force you to fill out. Don't go crazy on the calories, the body can put down fat much faster than muscle. You just need to create a sufficient demand for calories to be partitioned to lean tissue.