Are you sure its all breathing technique, and not swimming? As mentioned, perhaps its an efficiency of stroke issue.

Also, how much are you kicking? Kicking uses the biggest muscles in your body, therefore the most oxygen. Try kicking much less, and smaller kicks if you aren't already.

As for breathing, I alternate between every other stroke (same side) and every two strokes (alternating sides). I have been working on alternating sides more, trying to do an extra half-lap each time until I'm completely comfortable with it. I also find the more I exhale under water (breathing out nose and mouth) the bigger, better inhale I can take.

Happy swimming!