Constipation Treated With Ducolax, Holding Stool Due To Fear Of Pain, Tummy, Rear End Sore. Will Movicol Help?

My four year old was recently constipated (5 days ago). It was the first time and it was treated with ducolax and a glycerine suppository. Since then she has been holding on to her stool as she is fearful of the pain. she is in constant agony as her tummy and rear end are sore. She does try to go to the loo but is also nervous. She has been on movicol for two days npw and has not had much luck. She has only had one small movement that was large but relatively soft. Do I continue with movicol as the dose goes up to 6 sachets today. WHEN can I expect the movicol to work?