Swimming

Sunday is normally my treadmill and swim day, but I've developed tendinitis in my right Achilles tendon and have decided to avoid the treadmill for a couple weeks until it heals up a bit.  So my workout tonight was all swimming!  I wanted to stay in the pool for a half hour so I broke up the laps with some pool running to give my legs a workout.  It is HARD to run in the pool!

Anyway, I swam a total of 650 yards tonight when all was said and done, but I'm a bit concerned about my breathing.  I find that my most efficient stroke is freestyle, breathing after every 4th stroke.  However, after about 100 yards I find that it becomes harder and harder to take a full breath to carry me forward and my throat starts to feel constricted.  Breathing after every other stroke is a bit better but it throws off my rhythm and slows me down.  And in general I find that my breaststroke is extremely slow as well as more tiring.  Is there anyone out there with advice on how to improve my breathing?  I think this will end up being the limiting factor in my ability to complete the triathlon in August, so I'd better find a solution to this problem!