Effortless Swimming shares feedback video that reveals the importance of timing your breathing when free style swimming. Are you breathing late? Are you using your hip properly? Are you using your head positioning to increase your momentum?
The timing of your breathing can really affect the quality of your stroke. Remember when the "hand enters you should start to turn to your head and when you want to turn your head back around is when you start to pull through or start to catch on that arm that had entered out in front."
Focus on keeping your head centered and getting the right amount of air intake. Know that the power position is when your eyes and head are down.