how to swim faster?

Question
i learned how to swim since i was 10 years old. now i am 19, and i still love swimming very much.
since i seldom go to swim,once in a while..because too busy in study and transport problem..the speed is dropping fast..and of course i will be tired faster.
now i want to train back my speed...no...i want to train to swim faster..there was a period of time i go to swim constantly but my speed didn't seems to be improving..isn't due to the wrong style?(i had a coach for 5 years and i know all style,except butterfly style is quite hard,because tiring)
how to train to swim faster?for free style.and other style as well.i used more strength to swim but it seems no different at all.


thanks for helping!!!

Answer
Hi-
You can train to go faster, but the big drawback is that you have to be able to commit time to it.  To go faster you have to train more, once in a while is not enough.  If that is all the time you have, all you will probably do is get back to the speed you had before.  As you are getting older, it takes more work to be able to train your body to get faster.  As to your not getting faster when you had a coach, there could have been some small problems with your stroke technique that your coach wasn't seeing.  The best thing you can do at this point is to find somewhere to train with a coach who can get your strokes efficient again and to give you some training ideas.
Hope this helps a little,
George