Some thing that might help you is a scale, and my PLAN or fitday.com. I just bought a digital scale at Bed, Bath,and Beyond, for $30, with auto zero. I put my plate or bowl on it zero, add my lettuce, write down the weight, re zero, add whatever, record the weight, ect...
This really makes it quite accurate. Even weighs my dressing. I cooked all my life and I am very good at guessing measurements. Even I was off on meat portions, by quite a bit, I said 10 oz and it was 6 oz. So I will continue to use it until I know I'm in the ballpark. Lettuce I was off, also. Just an idea, hope it helps...Bru