The flye is tough at the bottom of the movement but easier at the top. To match the strength curve and build more muscle, add manual resistance at the top.
Because of the strength curve of the flye, the resistance is heaviest in the bottom position. With every degree your arms move up, the lever arm gets shorter and the exercise feels easier. At the top, not much tension is placed on the chest. This is suboptimal.
To get more from this exercise, use a training partner. Have him place some manual resistance against your arms starting at about the middle of the lift. You'll get a full-range challenge on every single rep and trigger more muscle growth.
Thibs thinks you're looking kind of small lately. Says your girlfriend's been bad-mouthing your physique, too. Fortunately, he's taken pity on you and come up with some new movements for you to try.