Hi Ada
In addition to the good things already recommended here, like the psyllium and prunes etc, I would also like to mention magnesium citrate as it is a really good and natural laxative. Just be sure you are allowed to take extra magnesium with whatever meds you are on.
There are a couple of brands of mag citrate powder that one dissolves in water and get a fizzy good tasting drink. We use Natural Calm and I think mrsD also mentioned one called Ionic Fizz
A cup of that at night promotes good sleep and a regular morning movement