What if the fiber doesn't work for the stool getting stuck???

Can make worse. Stop the fiber or add a osmotic laxative such as miralax. Miralax or polyethylene glycol 3350 is a powder which is dissolved in liquid. You can take MiraLAX 17 g once to twice daily. You may not experience any effect for the first day or two but continue to use it. Main side effects of MiraLAX are dehydration from diarrhea if you have too great of a response you can lower the dose.