I have had severe chronic constipation, IBS-C for a long time too, I so understand the struggle and frustration. All the fiber supplements made things worse and I cannot tolerate a lot of water because of intersticial cystitis and some incontinence. My G.I. doctor finally gave me samples of Linzess a week ago and that did not work. I ended up un E.D. on Monday after trying enema to help discomfort and all the straining caused a rectal prolapse. I am now trying the Miralax again twice a day, Senna 8.6 mg twice a day and lactulose twice a day. Now I am afraid that I have another proplapse with bowel movement, I have appointment with colorectal surgeon in August.