That must mean you are in very good condition, be proud of that!

One drill that helps with bilateral breathing is single-arm swimming: swim one length with only one arm, holding the other one extended in front. You're supposed to use a pull-buoy with it, but I do it with extra-super kicking to make sure I am getting a cardio and leg workout (because, you know, the cycling and running aren't enough leg-ercise !). I do it one length breathing right-one length free-one length breathing left-one length free, and repeat as much as I feel I need (usually twice). When I'm doing stroke drills I breathe every stroke, even though in regular swimming I try to breathe every 3-6 strokes, because the focus in on the mechanics and not on the rhythm.