Must a person suffering from urinary and flatulence incontinence and obsessive-compulsive purification change his underwear for every prayer, or is it sufficient to place a barrier on his clothes only at the time of prayer?

"One afflicted with urinary incontinence must take precautions by tying a cloth around the area to prevent the spread of impurity. The Malikis do not obligate this, nor do they require him to re-tie the bandage for every prayer. If the impurity spreads onto the clothes, he must wash the soiled area for prayer, unless he is unable to do so, because avoiding impurity is a condition for the validity of prayer, provided one knows and is capable. This applies if the incontinence is real; however, if it is merely obsessive thoughts, they should be disregarded."