I believe psyllium husks are very good if you are constipated, so some people use them for this purpose. It makes things very 'regular'. My only concern is perhaps they would make things on the firmer side which isn't what you want........

Perhaps try the kiwi-fruit, and if that doesn't work, then a trip to the chemist as I mentioned before to see if they can give you a softening agent.

I hope you find something that works!!!