Equilibrium

Let's see, I'm 16, around 5'5" (last time I checked at least) and weigh around 120 lbs.

From what I can tell, my weight is in the average for my height/age, but I am still deeply unhappy with my body.

I do some generic exercises and stretches as part of my college course (acting, for the record), and more or less everyday I walk for about an hour and a half.

I do at least 100 sit-ups everyday and am about to start lifting weights.

I have a fairly healthy diet, as I eat very much in moderation.

I just wanted to see if anyone had any ideas or recommendations for me as to how I could improve my exercise and improve my body.

Personally, I see myself as being fat, but this has been dispelled by people I have talked to, so I don't know whether the majority of my problem is physical or mental.

So, any suggestions would be very much appreciated. Thanks.