Don't worry too much about the stroke, it helps but if you are happy with it stick with it.
The best thing is to break your swims down into short hard sessions, so do a target distance in a set time (say 200 metres in 2 minutes) then have a 30 second break and repeat until you run out of time / steam. If it takes more than your target time after a few repeats have a ten minute easy swim and get out.
You might also try one length full speed. I mean really hard, then 3 easy ones and repeat this till you can't do any more!
Don't worry too much about the stroke, it helps but if you are happy with it stick with it.
The best thing is to break your swims down into short hard sessions, so do a target distance in a set time (say 200 metres in 2 minutes) then have a 30 second break and repeat until you run out of time / steam. If it takes more than your target time after a few repeats have a ten minute easy swim and get out.
You might also try one length full speed. I mean really hard, then 3 easy ones and repeat this till you can't do any more!