Your frænulum will
always look a little "short" - that is its nature. Look at the pictures on foreskin.org
by way of reference. The fact that you can readily retract when flaccid, if
you can do so to the extent that there is no "bunching" behind the glans would suggest that you have little or no need to stretch the frænulum.
If you are reasonably confident about this, then you need not be too concerned about frænulum stretching and of course, if it later appears to be a problem, then there is no reason you cannot proceed to do some stretching of it, you will have merely lost a little time.
Unlike other places where you may have received "advice" on stretching, we do not
advise you to do so by pulling the foreskin back (over an erection), nor do we advise doing it in the shower, because it requires time and your reasonably full attention and two hands - if you have not yet done so, you need to do the deep
reading through many index pages' worth of discussion "threads" here to understand just how
to do the stretching. To do this in the shower would be a shocking waste of water and no doubt, annoy your family no end.
You should definitely
not be exposing your foreskin or the area under it to soap which will
cause dryness and is responsible for almost all of the "problems" people report with foreskins. While yeast is a cause of problems, I diverge from Jim in doubting this would be the cause of your present concern about dryness - soap and too much
rinsing is more likely.
On the other hand, I doubt that water flow masturbation in itself (even chlorinated water) would cause any great degree of damage. I do wonder however, whether you were doing this (and presumably with an erection) with your foreskin retracted or what? In the more general sense, we are interested in the history of your problem - when you first retracted, whether you ever could retract while erect, how you learned about what you should expect your foreskin to do and any other detail.