Playing around with your breathing patterns can really help you to find confidence in your swimming. Knowing that you don't have to breathe every 3 strokes, especially when you're swimming easy will help you to relax better. Pushing the number of strokes up between each breath is a great way to train your lung capacity.
Warm up: 8 x (25 Body Position Kick or Scull / 75 Freestyle)
[400 Freestyle Easy (Change your breathing every 50, start with 1/2, then 1/3, 1/4 etc) - 20sec rest
400 Freestyle Easy (Breathe 1/5) - 20sec rest