Here are a few things that help with that (had a problem with it all my life....both really....guess I might have IBS)

take fiber pills (there's plenty of sf kinds out there and they don't taste)

Drink lots of water

eat a few malitol containing sf candies to start you off (two little bars should do the trick....take heed though...they work fast)

aloe vera tablets also help you to go

Hope these help....you may also want to pop in the IBS area as these guys deal with both extremes and will probably have some even better suggestions.