Breathing every 4th stroke

Swam 1250 yards today in 50 yard segments, and then a final 100 breathing every second stroke from the right side(every 4th stroke total). I can do it for a little bit, but then I become very uncomfortable as the carbon dioxide builds up and I feel the need to breathe. I have to swim very slowly to limit energy use. Still, I seemed to get better as the workout went on. My balance is much better when I swim this way. I will try to keep this up for awhile, and then try some bilateral breathing using the left side (every third stroke). I think in the long run this will really help my swimming.