Why is it so hard for me to get muscle definition?

First, my diet is definitely in check. I eat 6 frequent meals a day consisting of chicken breast, brown rice, oatmeal, egg whites, sweet potatoes, and tons of veggies. I don't season anything so there is no salt and as less fat *** possible. And my workouts are crazily intense... I don't think they're intense i know it for a fact as i actually know how to lift unlike some who skip around muscle groups orbench everyday. I also do 1 hour of the stairmaster everyday. I'm trying to get into bodybuilding but i just cant seem to get the definition.