Well there are some good responses for your question, but my suggestion would be,
Usually swimmers just turn their head to the side with the arm that's pointing back (other arm is pointing ahead). Your body is already in a slight roll with the shoulder of the arm pointing back sort of higher then the other arm so it's natural to turn your head to that side and take a quick gulp of air. Watch the tapes of Olympic swimmers to see how they do it. You're having problems with it now because it's still backward to you but with enough practice, just like swimming, it'll become part of just a natural rhythm as you swim. And if they do it in the Olympics, it is probably correct. You might also want to check with your swim coach. I'm surprised no one has taught you this already if you are up to competition standards. Hope you will understand what when wrong for you.